Hey , in pd2 is harder because dracs doesnt give life tap .
I think that you need alot of ll or wand with lifetap

Also you need to have prevent monster heal or open wouds to kill dia because he is healing .
Overall the gear you have in my opinion needs to upgrade a little , better weapon , zaka etc and then could work .
I remember a month ago me with the sorc and a friend with necro trying to kill ubers ...we killed mepho then baal and diablo was the problem because we both are mages and he healed all the time. The only way to kill him was with mercs openwounds but he dies easy there.
Now i made feral druid (withoutnmf i find more items then with 600 mf sorc what a waste bte) and can solo ubers and clone with only holding a mouse button :))