I'm not really sure what the real purpose of the thief is in this game. I've played games like DA:O where you just HAD to have a rogue in the party or you would not be able to unlock anything. But in this game my Ranger just shoots traps with her bow and my Cleric just carries some extra sticks just for bashing locks. Both can sneak apparently very well. Just not sure what the need of a rogue/thief is in this game anymore. There is nothing really unique to them.