Below are some tips for heretic's in both groups and solo play. Some of these tips are spec dependant so some may not apply to your heretic.

Group tips

If you're a caster heretic your job is simple, destroy any casters, and especially go for casters that can DoT first (otherwise they could permanently interrupt you). If you're a tank heretic then simply join the assist train.

The secondary job of a heretic is to disable an assist train this is really easy to do but very dangerous for you, make sure you're at a good range from the assist train and that no casters are around you then AE-DD-snare this will mean that they are snared by 70% while you maintain the focus. This is excellent to give your assist train a way to catch up with their assist train and also to stop their assist train from killing their original target/s.

If someone dies and the battle is still ongoing if you're currently available do monster rezz quickly as long as you're past the "mezz them!" stage. If you do monster rezz before the mezz stage is over then the monster PBAOE will remove mezz on them.

Damage shield - don't do it, it can break a root on an enemy.

Buff sheer proc - This generally overwrites a cleric's heal buff and also prevents SoM/Mad scalar's etc proc's from activating properly (presumed a bug), the buff sheer proc is not worth it unless you're solo.

Solo tips

If you're solo ignore the tips about damage shield and buff sheer proc from the group tips above. Instead you should fully buff yourself with all of your conc buffs, self buffs, damage adder and damage shield and also your buff sheer proc.

If possible open your battle with a single target uninterruptible DD (the one without the snare) try to maintain it as long as possible.

If the enemy gets within melee range do your single target snare run as far back as possible from them hopefully to 1500 range then do your single target DD again, this time it is upto you if you use the one with or without snare, personally i would do the one without snare as the damage is much higher. Once the enemy reaches melee range again use your single target growth DoT then enter into melee with the enemy.

If a stealther attacks you then begin with the insta-snare-->run-->DD tactic. If the stealther used a poison/DoT then purge it immediately. Most stealthers have much lower HP than other classes so your DD should be very effective.

Single target uninterruptible DD should always be used while solo as it cannot be stopped by casters other than with DoT/CC/nearsight.

If you get a DoT on you either purge it or enter melee range as quickly as possible, a DoT will interrupt your focus DD at every tick of the DoT.

+range does not effect focus DD's of a heretic, there is no point having this on your armour.

If you encounter a group vs. group battle while you're out and solo and do decide to leech do not under any circumstances use your AE-DD-Snare. the AE-DD-Snare will make the group very angry at you as it will break any mezz/root they do plus it is not a good method of leeching. The AE-DD is very low damage, if you do intend to leech then use the focus DD, this will do the most damage and get you the most RP's.