congratz!! lilith is imo much harder than the actual UT. but that might be because i killed the ubers so much more often than the minis.
you could watch a few videos of UT-runs to get the feeling about the easiest way - which is to lure them out one by one at the upper end of the houses, then move them in the direction of where wirret would be lying. for uber mephisto you might want to get a 3 socket helmet filled with orts (iirc his attack was lightning, but i canīt remember) the others shouldnīt trouble you too much, once heīs dead
I did UT with a necro way back and i think my gear was like this:
Shako with um
Homunculus with um
merc had eth infinity
guillaumes with um
and armor was eth fortitude
also had a lot of summon skillers with fhr, resists and other smatterings of life, res etc.
summoned whole army up including mages and skeles and always use clay golem. urdars i got from durance i think.
tp in and go north then come down along the left handside of the north building, lure out meph and tele on top of him and walk back about half a screen, i used terror to scare away the cronies and use decrep on him, he should hardly be moving now due to decrep and clay golem, when he is on a low amount of health use amp damage to speed up the last amount of his hp. this should take around a minute ish. if revives get out of control just tele back on top of him and rinse and repeat.
kill of the remaining minions and then go up and clockwise til you are near the exploding cow and then lure out baal. he should be a breeze if you use the same tactics. then go engage diablo who drops easiest of them all. whole run should take no more than 5mins.