Late to the party but I just wanted to say I have a Rogue and a Warlock in a 4-person group and with the way the spellbooks work I definitely wouldn't want to rely on only magic to cover the thief skills. Magic will cover the occasional case, but in particular for unlocking and secret door-finding the Rogue is far from redundant. Also, don't worry too much about starting affinities for spellcasters, they give you a small headstart but you can overcome them pretty quickly in my experience.
Might try the Hero path next if I decide to start over with v2... those companions are looking pretty juicy.