My preference is Complete Expert, but I'd be fine with Complete Scoundrel, too. Not a one of the other options even remotely appeals to me.
Personally, I'm not overly happy with Complete Divine or Complete Arcane. Neither one really fits with Complete Warrior. You've really got two naming styles. CW is "Complete" + noun. CD & CA are "Complete" + adjective (or something like that). Complete Arcanist would work much better for CA, but I'm not sure what I'd have chosen for CD -- maybe Complete Divinist.
Of course, that's 'cause I like the Complete + noun form better. Going the other way, CW should have been Complete War. The rogue book could be Complete Expertise.