What is a Witch Hunter's Target?

I have been playing my Witch Hunter on Badlands on Tier 2, and as always, I have success as part of a well led WarBand (Thanks Dainain), but I struggle in scenarios.  At level 19 and 20 I was still unable to kill shammans, zealots, or DoKs out of stealth.  Some of that is gear, I have a less than optimal rapier (Renown purchase at 25 DPS) instead of the higher T2 or scenario reward weapons at 29 DPS.  I'm hoping that ANYONE reads this and can help with some advice.

My rotation and such is as follows:
Out of stealth, Sudden Accusations...followed by three Torments then run accusation of Burn Armor for the large DoT.  I am using bullets of purety to half their outgoing heals.  I then hit Silence the Heretic, followed by more Torments and then accusation (normally Absolution)...I rarely have them down to half health at this time and then their healing and HoTs kick in and I can't outdamage their healing.

I'm positive its the player and not the class...so any tips and suggestions?

On a side note, I was playing on Black Fire Basin and I got to do what Witch Hunters do best...kill people along.  I would hide behind a tree near the route back to their base where they would plant the flag...Order was getting farmed short of the flag...I managed four solo kills on flag runners...all Melee DPS types.   Isn't it sad I can kill a high damage output character...but lose miserably to healers?  Managed all the kills with only one health potion as well.  Felt like a good use of my skills as I delayed them winning by almost five minutes...more of a personal victory although I did pull pretty good experience and renown out of that scenario.  Too bad I only managed one emblem for my scenario reward.

Fortunately, I leveled him out of Tier 2 in time for the Battle of the Badlands, Tier 3 night...so hopefully I can follow more competent Warband leaders than myself and have Order be successful.