Do characters have an IC concept that doing quests that give XP will give them some sort of "reward" with their guildmaster? Say an evil character, whose role stipulates that he doesn't help people unless he's getting something in return, were to do a xp quest that involves helping some hapless npc. Would it be against his role, or would he have the understanding that he was going to "get something" for running this npc's errand? Or does it just depend on how explicit the particular quest is?

When playing evil, the only time I do quests is if the NPC tells me up front that I'll get something for running the errand (or if the quest is just obviously evil in nature). My character weighs his options, and if it seems worth it, he'll agree to perform the task. Without that up front statement, I won't do the quest, though I could think of a few ways to RP it so I would be justified in completing it.

Yeah, pretty much what I figured. I can rationalize helping out an npc mob if I, say, kill them right after completing the quest.