I did act 1 - 3(Hell) with help. I'm not sure I could stand taking a single element sorceress through Hell.
As long as something isn't immune I can usually tele-orb-tele-orb-potion-etc and It's just a matter of me avoiding their attacks. I also cast-move-cast quite a bit, and then teleport ahead then step back to get the dummy in front of me. All standard stuff, I assume. :-/
The formula takes level and shield type (and bonus) into account, so it's doubtful that anyone
can give you a solid answer right off the bat. Easy version: for the shields suggested here? You
probably need around +150-200 dex at ~level 90 ish. Ballpark, I'm too lazy to calculate it.