He usually does pretty well but he's performed best when deployed not too far ahead of the main crew. The temptation is stick right out there but unsupported he can get into "unhealthy" situations.
I got excellent use out him in my last game against the Ortega's. Both of us had claim jump, & were going for the wooded are in the centre of the board. When got there I froze it over each turn to prevent the other crew entering & then arced decembers curse through him to take full advantage of his ability to draw LOS through terrain. Even his worst performance yet was pretty good. He got bundled by 2 mature nephilim but it took them 2 turns to kill him.
His zero action of Eat your fill really helps him last through the encounter as well as defeating an enemy in combat you then get to go back to full health, brilliant!
I'd say my main gripe with the Acolyte is cost. At 6ss he's realtively expensive as Cult of December henchmen go but if you bite bullett & play him right he's dynamite.