Mastery of Pain
Now that the prerequisite has been removed, this is a very attractive ability. For just four points you can get an additional 9% chance to critical hit on melee attacks. Your criticals in RvR are limited to an extra 50% damage, but even so MoP 2 is equivalent to an extra 2.25% damage overall (assuming an average critical of 25%).

Purge
It was pretty much a must-have ability before, and that hasn't changed much. It's hard to overstate its usefulness. Even the first level of Purge, 5-second-delay and all, is a frequent lifesaver.

Avoidance of Magic
Already it's been nerfed, and it's not even released yet! AoM no longer affects crowd control spells, meaning that Mythic has essentially done nothing to decrease the CC disparity between pure melee classes and hybrids. Despite the nerf, since many casters are now getting Mastery of Magery (itself nerfed, but not so badly), AoM is almost required to offset that greater damage. Eventually, getting AoM4/5 is a very good idea.

Long Wind
The ability itself hasn't changed, but it is now more useful because of the greatly improved Tireless (Tireless now being at least five times as effective as before, not to mention free). Better Tireless means more endurance, which in turn means Long Wind helps for a longer period (you might also think better Tireless means Long Wind is redundant… but the two abilities work very well together). Long Wind 2 might be a good investment if you spend a lot of time taking long walks or if you need to chase enemies down mid-battle very often; LW 1 is worth it for everyone.

Mastery of Blocking/Parrying
Like many realm abilities in New Frontiers, the first levels of these are not so useful as they once were (levels 1 and 2 each being 1% less effective than their pre-NF counterparts). But they're still very nice, considering how many spec points they can compensate for. Depending on what type of Reaver you are, you will probably want different levels of these abilities (or of one of them, tailored to your enemy of choice):
1. Slam+Levi Reavers have the least need for these abilities, as they already have a high shield and can simply Stun someone, at which point defensive abilities aren't terribly helpful.
2. 50/50 Reavers gain a lot from these two RAs, as they still go out into the fighting but don't have the high shield skill.
3. Reavers who help their side by protecting casters and healers have the most need for any defensive abilitiy, these included.

Augmented Quickness
Despite any number of people who believe otherwise, Quickness helps. And it's been proven over and over again that, at least for a Flexible Weapons Reaver, Quickness helps a lot. Depending on how often you use Leviathan as opposed to other attacks, you could conceivably increase your DPS by a third - possibly more.

Reavers with foresight (who put points in Quickness on character creation… and aren't Inconnu) should be able to hit the Quickness cap of 250 with Aug Quickness 2. Others will find it more difficult, and likely not worth their time.

You can use a weapon speed calculator at http://www.classesofcamelot.com if you wish to figure out how much affect extra Quickness will have on your swing time.

Dual Threat
Statistically speaking, you're better off getting both Mastery of Pain 2 and Wild Power 2 before thinking about Dual Threat at all. After that, it pretty much depends what you want to focus on - if you want to crit with both melee and spells, DT isn't bad.

It does not, however, affect a couple of things that a Reaver could use crits on: debuffs and style procs. And except for the DoT, criticals are limited to 50%. If you want to get more damage out of your lifetap shout, DT will help; but you're probably better off ignoring spell criticals after Wild Power 2 and simply getting Mastery of Pain 3 rather than DT 1.

Augmented Strength/Dexterity - Those who want to get the absolute maximum amount of damage in melee should focus on both of these, in order to increase weaponskill. A side benefit is that the damage of the Leviathan proc will also increase. For any truly noticeable increase you have to spend a goodly number of points, however; only the most offense-oriented will want to get both. Reaver block bots, or anyone who makes their way as a caster/healer guard, might want to focus on Augmented Dexterity alone, as it will increase your defensive abilities

Serenity
Running those chants can get difficult after a while - and in NF it gets worse, with several-hour-long keep and tower battles during which you may find yourself doing nothing more than hitting the enemy with your DoT and lifetap shout every 30 seconds. 30 second timer notwithstanding, that can end up with you OOP very quickly.

But Serenity is hardly necessary if you have a Font of Power nearby - which is the case in most long-term fights these days. Serenity comes in handy mainly when you have to run chants for a long time in a pitched fight out in the middle of nowhere - not exactly a common occurrence.

Toughness
I've said that low hit points are one of a Reaver's greatest weaknesses - and despite all the changes the game has gone through, that's still true (although a fully buffed and extremely well outfitted Reaver can push past 2200 hits). Toughness helps with that problem, obviously.

The more Toughness you purchase, the fewer hit points you get per RA point spent - from 25 points at level 1 to only 12 at level 5. Only the first couple levels are worth getting, even if you're concerned about your hit points - beyond that you will do better to spend points on other defensive abilities. Reducing damage is just as good as being able to take more of it, after all.

Veil Recovery
This ability used to be a joke, much like Mastery of Water - but now it is conceivably useful. If it reduces the duration of the RvR-specific resurrection sickness, getting level one or two of this ability will be a good use of points for those who want to get right back into the fight (and to be able to do some good once they get there). There's no word as to whether Veil Recovery affects the RvR rez sickness, however. Patch notes seem to indicate that it does not, but if that's the case Mythic has no reason to keep the ability around.

Lifter
Yeah, it's a weird ability to put here. It's been ridiculed, treated like its unwanted cousin, Mastery of Water. Why should you even consider it? What good is carrying more stuff, since all the stuff you really need only takes up 20% of your normal capacity?

New Frontiers is focused on siege. Classes that cannot do decent damage from range have little part in a keep siege other than to run a siege engine. Siege engines are heavy, and they get destroyed, so you might want more than one. Lifter might allow you to carry 3 or 4 engines rather than 2 or 3; fully buffed and with Lifter 5, you could probably carry 8 siege engines or so (probably making it a good ability for a bot, at least). Lifter still isn't a great ability for most of us, but for those who are going to be doing a lot of sieging, it might be worth a try…

Mastery of Focus
This RA has been put forth as a possible aid to Slam Reavers who often face high resist rates on their spells. Others have speculated that it is a way to increase the chance of the Indigosnake proc actually landing. The latter use may or may not work (MoF may not affect style effects at all), but the former certainly does.

Unfortunately, the level of the spell changing for resist purposes won't make any difference in the actual effect - if you were hitting for 100 before getting MoF, you'd hit for 100 afterward - you'd just do it more often, as a result of fewer outright resists. Slam Reavers who at least want their debuffs to land should probably consider level 2 of this ability.

Mastery of Magery
More damage is always good, right? Sure, but MoM comes at too high a cost for too little benefit for Reavers, who aren't going to be doing a lot of spell damage regardless, with those overly long 30s timers. Say your damage on a Lifetap goes from 180 to 230 or so - that's an extra 1.6 DPS, at a cost of 34 RA points. You'll get smaller benefits from other spells - Wrack, the DoT, probably the Debt to Arawn proc - but it won't be significant even adding them all together.

The saving grace for MoM could be its effect on the Levi proc. I'm not sure what logic Mythic is using to decide which RAs should and should not affect that proc, but apparently it's a spell when it comes to MoM, and not a spell when it comes to Wild Power/Dual Threat.

Wild Power
At the beginning of the NF beta, this would have been one of my first recommendations. I would have raved over its extraordinary utility. That was when the style effect portion of Levi could crit. That has changed; now no style effects or procs can crit.

Spells crit'ing is nice. I like it. But as much as I like Soulrending, the idea of using it to do significant amounts of damage is laughable. Spells on 30 second timers simply can't create much DPS, crits or no crits. What was appealing about Wild Power was that it allowed Levi to crit. The proc/spell effect of Levi is one of the biggest (if not the very biggest) forms of damage for a Flexible Reaver. Anything that allows you to get more damage out of it is obviously a good thing - something that allows you to get up to 50% more damage out of it on some hits is a very good thing.

Without that, WP is a toss-up. Certainly I'd go no higher than WP2 unless you're a Soulrending fanatic.

Thornweed Field
An active offensive ability at last! The only other one available to us is the onetime Unquenchable Thirst of Souls, now renamed Soul Quench, which we get for free at RR5. TWF is attractive simply because of its differentness - Passive abilities are nice, and Purge and some other active abilities are very helpful, but they don't involve a lot of action on your part.

The first level of TWF, like the first level of most active abilities, is fairly useless. The damage is extremely low and the duration is extremely short. But the upper two levels will allow you to use a sort of crude crowd control as well as do some very nice damage (250 damage x 10 pulses in 30 seconds x a large number of people in a small area - the inside of a tower, say - for the level 3 version). It'll require more intervention than passive abilities, obviously, and won't be available to you all the time… but if you're willing to spend a fair amount of points on it, you'll be rewarded.

Determination
Be careful what you wish for, they say. Determination is a good example of why that saying exists. Reavers - and all hybrids, for that matter - hounded Mythic ceaselessly to get Determination added to the class. Time and time again the request was denied. In NF everyone gets what they want… sort of.

While we now get Determination, it is not the Determination it was before. It doesn't reduce CC duration by 75% if you get level 5; it reduces it by 34% (one percent per RA point spent)! The new Det isn't even half as effective as the old Det. On top of that, the disparity between hybrids and 'pure tanks' in terms of CC still exists, in the form of Stoicism. While even Stoicism + new Det isn't equal to the old Det, it's a good deal better than new Det alone.

A 34% reduction to CC serves no real purpose; by itself, it isn't enough to justify the cost. Rarely will reducing CC duration by a third save you; reducing it by three fifths, like pure tanks can do, is another matter. We got Determination, but now we don't want it.

Augmented Constitution
At no point does Augmented Constitution become better than Toughness. More hit points are good; but Aug Con gives you little boosts like 13 or 45 hits. The argument most give for Aug Con is that each point of con is worth more as you get more of them; so when you are buffed, Aug Con will give you more hitpoints than when you are unbuffed. Even so, however, it's really a waste of your points.

Whirling Dervish
It sounds exciting - double your damage for 20 seconds! But if you think about it, this is absolutely terrible for Reavers. Reavers rely on styles to do most of their damage - even doubled, base damage isn't very strong. And using Whirling Dervish means you give up the opportunity to use any reactionary or positional styles.

The one use for the ability is when you are completely out of endurance - but with the new Tireless, end pots, and Paladins, that shouldn't happen often enough to merit spending even 5 points on the ability.

Second Wind
This is useless for a few reasons: Tireless, endurance pots, and Paladins. With those available to you, running out of endurance should almost be a thing of the past.

Ignore Pain
We've all come to love or hate the previous Ignore Pain - personally I hated it, as it cost me any number of fights and was one of the abilities that people never felt leaving the PK without. Previous feelings aside… I still don't like it, but this time because it's not useful enough.

You have to spend 30 points on it to get an 80% heal available every 15 minutes; 15 points to get a 50% heal; 5 points to get a 20% heal. A 20% heal is almost negligible (you can get that much lifetapping someone's undead pet); 15 or 30 points for something usable every 15 minutes, in New Frontiers' environment of almost constant fighting, definitely doesn't appeal.

First Aid
The very simple problem with this one is cost-to-benefit (just as with Ignore Pain). The points required don't come nearly close enough to being worth it - especially considering the fact that if you drop out of combat for any significant period of time, you ought to have a healer nearby doing First Aid's job for you.

Mastery of Concentration
We get this spell as a "power user", but obviously it's not really meant for us. We only have one spell with a casting time - Debt to Arawn - and since it lasts 20 minutes, stopping to cast it in the middle of the fight isn't really reasonable.

The Empty Mind
It's the problem with active abilities, come up again… for about the same amount of points, you could get a passive ability (Avoidance of Magic) to do the same thing all the time, rather than for 45 seconds out of every 600. It wouldn't be a bad ability, if AoM were removed, but it simply isn't up to par.

Mystic Crystal Lore
MCL could be useful as a sort of last-ditch effort to kill someone - you're out of power, your Lifetap is available, the enemy is almost dead. Except, of course, that you can't use it in combat; you'll be better off just drinking a power potion, or maybe finding a friendly Necromancer or Font of Power.

Raging Power
I'm not sure how to explain why this one isn't worthwhile. It seems to be so simple I can't put it into words… it's sort of a combination of Ignore Pain and Mastery of Magery. Spell damage is such a small part of a Reaver's overall damage that getting an RA to allow you to cast and get that damage is silly, especially at the costs of this one.

Strike Prediction
It's a very odd RA… for 30 points you get an extra 15% chance to Evade (the difference between the 20% of the RA and the 5% you normally have). Of course, your caster and heavy tank friends get a decent improvement if you spec lower in it - but with a duration of 30 seconds, and Evade not being all that useful for those who will benefit anyway (it's not going to keep casters alive, and heavy tanks have other defenses), there are much better things to get.

Augmented Acuity
It increases Piety, which increases spell damage. But see Mastery of Magery for explanation as to why that isn't as helpful as you might think.

Ethereal Bond
50/50 Reavers know well the situation: You've been casting spells for a while, maybe running chants or even twisting. Then you run out of power. This happens fairly quickly in part because Reavers do very little to increase their power pool - rare is the item template with a good amount of Piety, and pretty much nonexistent is the template with Power.

Ethereal Bond can make up for that, but it requires a significant investment to be noticeable - at least to level 3 (which is about 5 extra pulses of a high-level chant). Anyone without 50 Soulrending shouldn't have to worry about it; even those with 50 SR should probably steer clear. In any long-term fights there's usually a Power font, which makes a higher power field to begin with pretty much unnecessary.