I feel sneak is utterly useless. Mind you, my friend and I play a dex rogue and a mage generalist, but he never uses the sneak attack. Everything dies so incredibly fast in this game, so there's really no need for it. You will need it of course, if you want to min-max!
Actually, now that I think about it, my mage sneaks more than him, because I like to initiate the combat with a ninja-skeleton.
