Ive got -20 and below in the past
I got a tip play a bard, speficaly an blade, or an swashbuck, and get use all item for both of them.
Bard: (use all item)
+4 elven chain i forget the AC
ring of gaxx +2
Ring of protection +3
Boot of phaseing +2
Cloak of the sewers +1
dex 19+ by the end of the game i had i think 20 dex
one from tome in bg, 1 or more from other item and stuff in tob *shungs* also lost some dex in hell also so that changed it to.
Blur multiple time +1 each time, if you don't have the patch that fix this bug.
then blade's defensive spin +10 ac
hehhhehehe
do the same with swashbucker, but forget the blade defensive spin and blur cause the swashbuck don't cast spells unleast its a dual, anyway the swashbuck get extra ac every so many level so that makes up a bit.