Personally, from a DM's perspective, from running a group of 4 with 2.5 leaders (a pacifist cleric, a taclord and a chaladin - the 4th is an wizard), it can be really frustrating - its really difficult to make an encounter that feels challenging without making it a potential TPK, given the multiple healing triggers that can be thrown around every encounter.
I can make a recommendation for this sort of party composition. Provide more scenarios where "kill 'em all" is not the ultimate goal. Challenge them with time limits. Get to the time bomb before it explodes. Make the objective to not let anyone escape and warn the rest. Or give them a hold the line type scenario. Another good way is to occasionally deny a short rest. Run one level equivalent encounter, have some of them get away, and come back with friends for another level equivalent encounter, giving the PC's enough time to mop up what they are fighting, but not quite enough time for a full short rest. These sort of scenarios will challenge their per encounter healing resources and their durability.
All else fails, kill the passifrigin cleric, have a purple worm gulp down his body, a souleater consume his soul, and wipe the memory of his existence from his friends with a gaggle of mindscramblers. (If anyone plays a pacifist cleric in my game, such will be their fate.)