Look for builds if you're set on a barb. I did this on HC pred2r on hc p8 and it took me a while even with decent gear. I think there may be a concentrate option that outplays frenzy in Ubers.
But if you're set on frenzy, here are some of the tips
1 you need a ton of AR, prebuff enchant with demon limb
2 howl is the key- in mini Ubers this works good enough, but there are PIs and a ton of other mobs as you know, so this is where patience comes in
3 original question -kongslayer, oath, obviously grief would be very helpful, you do need to cause damage, so I'd advise 1 grief or a solid oath at bare minimum. Stormlash is very rare so if you have it that could work, or cmoon pb
4 decrep- you can use a lawbrogner pb on main hand, but damage is low. Merc could have reapers or go with the new A5 frenzy Merc and give the pb, regardless you need decrep up
4.5 life tap it's a risk to go without, but decrep is probably better. You don't have guarantee hits like smite or concentrate and not high AR like kicks, so life tap only works if You're hitting. Decrep improves your damage and reduces what you take, since it slows enemies
5 still need regular mods like open wound to stop Regen and crushing blow to take out dents of health
6 I did this on lod with a SP mod that did not have minions in Uber trist, so take the howl challenges described above and likely multiply them.
D2:R