How about a pacifier? This role is charged with diffusing combats through any number of means (before initiative designating a standard monster or several minions to be removed from the fight via a good diplomacy/bluff/intimidate check or putting incremental conditions on certain standard monsters and minions the PCs refuse to attack in combat on a track like Turn 1 slowed/ Turn 2 dazed/ Turn 3 stunned/ Turn 4 removed from combat [which actually gives a nice depth to battlefield and almost makes these creatures hazardous terrain, forcing caution not to damage with sloppy AOE or be dominated by an elite or solo baddie on part of the PCs until turn 4 when these monsters are removed entirely]), placating social adversaries via skill challenges and some sort of role-based advanced challenge, a duel of wits or mettle in combat for some group advantage, a lessening of forces/morale or alternatively prior to combat with really good planning or trap laying.
Pacifiers add depth and dynamism to normal encounters and help counteract the grindy combats by lessening the number of foes before or during combat, and maybe some sort of mechanic where if a certain number are bloodied, or maybe an elite or solo bloodied, he can force all others to flee, or come to terms with the enemy. Not saying this should always be possible. No way you're doing this to Mual-Tar, but I could see it working on a lot of sentient adversaries.
