Man-At-Arms and Vestals (or Flagellants if you are bold) goes wonders here. A Houndmaster can de-prot him and bleed him, while a Shieldbreaker can use Aegis to block DMG and also do Piercing DMG to him. An Hellion can stun him and/or bleed stack, though not the most effective.
I would avoid Highwaymen (too frail and DODGE loses effectiveness after certains uses of his buffs), Occultists (his debuffs wont last), Antiquarians are a bad choice (its doable tho), graverobbers are not going to be much effective.
(2/2)

Run.
In 3-4 turns you can foresee the possible results of battles. If it is going downhill just run. It is one of the many lessons DD imposes, there is no fruitful heroic last stand or sacrifice. You have the wrong king of kits to deal with him, and your formation is ill suited for a attriction battle.
The best way to deal with this enemy is to either bombard him AFAP by pierce DMG/bleed DMG or to stun lock him to only allow one action per time. His buff is the least likely skill to be used but is aggravating to allow him to do so, it will mean DD's checks all time, raising your stress sky high, which ultimately results in failure.
(1/2)