To me Sorc seems like the cookie cutter for untwinked for the simple reason of Teleport, both to farm LK and bosses. But after Enigma I agree Nec should be the least gear dependent and pretty efficient.
Not too sure about skillers being an issue actually. CE is main source of damage which is not dependent on skill level, but only relies on +1 skill gear for more range. But range is fine if maxed plus some standard gear. Also while I have a Beast on my (twinked) Summoner, Hoto is basically just as good. At least it was in Cow runs, but I'm quite confident this should apply generally. However, if an extra Ber drops it would be cool to have an untwinked Beast of course.
I think for boss farming Andy could be a better choice than Meph for him, since you can raise minions there and use CE. Also the benefit from the quest bug as a side effect, and she can drop most of the stuff you would need from Meph such as Shako and +1 rings...
except for Arach, which might be a real pain to get with him actually. But then again he's good at farming alvl85 at high player settings where you can get it with some luck, as well as some runes here and there, and make good XP process at the same time. In fact, as opposed to my Sorc which acquired
all her gear elsewhere and has spent not more than 2 hours in AT/Pits total (!), I intend to spend a lot of time with him in lvl85 areas - once Enigma is done ofc.
But that's mostly very far away in the future since I really want to finish the Sorc first, which will take a long time still, currently some 30% into lvl 97. Until she hits 99 I'll only play him in between if Sorc runs are unbearable from time to time. One project after the other.