If this is really a big deal, have one of the Fighters take a few levels of Warlock. See the unseen and perhaps Hideous blow (extra 1d6 or 2d6 damage when you have to take a move action and so can't take a full attack anyways) Add in the warlock septer thingy from CA and you could be doing an extra 14 points of damage on a single attack (not useable with full attacks). Plus a ranged touch attack for 14 points isn't a bad replacement for a bow if you aren't a bow user normally....
Yeah, I know, I like the Warlock too much... But do consider it.