It is possible to end up fairly over powered as a warrior, as well, if you complete everything, make the best use of the bonus levels in the game (wishing well, imp world jug and to a lesser extent the blessing ceremony), reload for equipment, etc.
Merchant inventories reset every 10 or 15 minutes real time, so even without any reloading, you shouldn't end up too under powered that a change of tactics (etc) couldn't help, unless you really missed a good chunk of the game. Actually, in the old Larian forum Ariana described a playthrough trying for the lowest level finish; she did the blessing ceremony at level 12, so was level 17 at the start of the wastelands. This involved a lot of saving and reloading to get through the required fights (like the succubus), though, so she quit at that point.
