Thief is a deceptively strong class. None of its abilities look like much on paper, but they are all incremental abilities, that each give you a few % boost to some stat - except all of these also reinforce each-other. So you have slightly longer bars; but you also have more refills; and then those refills are more efficient; you do more damage; have more shops, gold, glyphs; so you have more CP (= even more of something, like today it was even longer Mana bar), and have slightly better purchasing options (not as good as a Tinker, but better than average). All in all, Thief is the "more of everything" generalist counterpart of the "everything quicker" generalist Fighter. Except, a Thief who has B2P or HALPMEH can go crazy with the synergy of having off-color refills that can be converted into your preferred color. Today I did a Faithless spell-monger approach, and went Dracul after everyone was dead just for fun. No heroics, but I played quite quickly (according to my standards), I still have really exciting things to do tonight...

"Thinker", just without the "ache".