Overconfidence kills (in combination with drow).
I played a bit, and had some problems with the dark-skinned ones. I broke the cardinal rule (save after every fight) and had to go back to my last save, which was the one I started out with tonight.
I wanted to wipe out the whole level without resting, and that turned out to be a bad idea. I took down all the orcs, all the orogs, and most of the drow, but Insane mode adds more drow in unexpected places. I ran into some where I wasn't expecting any (3 sellswords, 2 vanguards and a sorceror in the table room), and they killed my tank and had two of my spellcasters down to 20% HP - without killing any of the opposition. Whoops.
That magic resistance really bites. They fought off a Vitriolic Sphere, Ice Storm, MM, and Sunscorch without taking more than minor damage. Next time I'm going to lead myself in with the toughest summons I can get, and Shield of Lathander on the tank. What irks me is that I still had a SoL spell to cast, but I was caught off guard by the extra drow.