I vaguely remember encountering a coridoor Shambler during a dark-run using Ves/3xHWM, all of which just spammed DA for Riposte, triple-teaming the Shambler with auto-damage anytime he pulled off his retreat or advance AoE's. Alternatively, you can go for the comfortable bleed strat by dedicating 1/2 to maintaining DoT damage on Shambler while someone else kills/stuns clappers. After that, the occasional ShadowStun on a front-row clapper and/or the Shambler once in a while will usually stave off the huge clapper-damage.

I've comfortably killed Shamblers with my trusty old Vestel>Triple GR, usually with the Shambler being put to 50% via triple Lunge right out of the gate if lucky (and considering Shambler = insta-torch quench, you have the crit-rate to pull it off, usually). The only concern you should ever have is inability to kill Clappers (if you have no CC) leading to big damage or stress over time, or lack of backrow burst (if no drag or unviable/short-ranged Melee champs). Shambler is not overly resistant to either Blight or Bleed. Shambler's AoE / Spawn moves trigger riposte. All three (Clapper x 2 + Shambler) can be stunned & moved.

Darkest dungeon shambler spawn