My thoughts on Mance: he's a push-over who fights dirty.
Seriously, in my first playthrough he catches me off-guard with the sudden mana burn and health drain, so I answer with chaos avatar... and then he hits me with 15 corrosion and weakening, which quickly whittles me away since I lack any way to deal with it. Okay, second time around, and this time I'm packing WHUPAZ and the vampiric blade you Horatio wannabe. His drain hits at an inopportune time (I'd just used a schadenfreude), but I blast through. In comes the Earthmother's curse, which I answer with chaos avatar. Approaching the end I decide to gamble on last chance, which succeeds. It looks like I have enough resources left to do this with HALPMEH, and then he invokes GG item steal and it's game over. He catches me with a full tank of mana (19 mana - I had two mana boosts) but half-health, so I cannot proceed.
This sort of thing just pulls the rug out from the under the player in a very unfair manner, and being at the end of a 3-dungeon trial that's incredibly infuriating. Mance requires you to sequence your attack pattern specifically so you always have resources left over after each of his curses, without providing any forewarning of which resources he's going to take away from you or when. Once you know what's coming, though, there are more than enough resources you can accrue throughout this three-dungeon journey to smoke him and he's not really that tough. /rant
Proposed solutions: put signs in the dungeon that hint at what curses he invokes, and what health% he invokes them. The curse of Binlor is usually harmless, so it would hopefully tip the player off to check the other signs before the harsher ones hit.
Dracul would be very nice here, since you can get an absurd number of CP on that dwarf and sanguine could offer enormous sums of health (not to mention piety for blood swells), and this wouldn't be affected by the GG item steal. Too bad I seem draw nothing but JJ and Earthmother <_<