Why? That seems like saying all monks should be plotting against barbarians, and all rogues against paladins. I think we all know that characters can have more depth in their motivations than that.
I don't know about the Ur-Priests not being able to benefit from true clerics thing. I can't think of the last time the cleric has cast anything on the Ur-Priest, so maybe he never has. Then again, the Ur-Priest rarely needs it, as he can cast healing spells himself, you know.
As for all of your suggestions: Thanks! I'm thinking the Dervish could be a lot of fun, but I'm worried that he might not be "front-line" enough. Surely in his ability to do damage there won't be a problem, but is he really a "tank"?
I'm thinking Swashbuckler/Fighter to enter into Dervish, but I don't have CW with me right now. Would including Ranger be a better way to go?
Never done dual-weilding before, so this should be fun.