Have you found rogues to be super combat-effective? I've been running Astarion consistently for traps and locks, and I've found that he really takes a backseat to my warlock and Minthara in combat. Provided he can get in position to hide and pull off a sneak attack, he's more effective than Shadowheart, but only if I'm playing conservatively, i.e. trying not to use any of her spell slots.