I have a clvl 87 IK Concentration Barbarian. His main skill is Conc as mentioned with a few spare points in Whirlwind. My strategy when normally playing is to WW through a group of monsters bombarding me then finish them off with my powerful Conc blows. It decimates.
After a long while I finally managed to get ahold of three keysets. I had never played ubers before, and wondered how well my IK barb would do. I know players seem generally biased against sets, but the IK set IMO is the finest in the game and can stand toe-to-toe with some of the unique/runeword setups out there. (I socketed the maul with a shael and an um [for the Open Wounds--crucial IMO] and the helm and armor with Sol's for the damage reduction). Also, I know WW is most preferred for the build, but I really don't think the skill needs to be maxed with the IK set. I put enough points in it so that with +skills it has positive damage (since it begins as negative) and it works for me just well. Instead having maxed Conc, I have a huge damage bonus (450%, on top of mace mastery's 250%) plus a gigantic AR bonus (my AR is above 10k). My life after BO-ing is 3,900 or so. I felt like my character was juicy and strong enough to give a shot at the mini-ubers at least.
Forgotten Sands--this was the only stage where I didn't run into any minions. I entered the portal and Uber Duriel was not far away. The biggest pain with him was his unholy freeze, of course--made my attacks way slower. However, after a Battle Cry call that reduced his defense and damage (74% and 37%, respectively), I was able to own him without much trouble. Even when OW didn't proc, he wasn't poison immune so the inherent poison damage bonus on the maul with the IK set was enough to stop him from regenerating.
Furnace of Pain--aptly named, because not only did I have to fight through a plethora of enemies to get to Uber Izual, there were the dreaded Oblivion Knights! Gxd, I hate them sooo much. I switched my attack to Bezerk to avoid the IM agony, and it worked fairly well because, thank goodness, I did not run into any Mana Burn packs. It would have been death of I did. When I finally reached Izual, he died faster than Duriel. Without the unholy freeze I was able to attack at full Conc speed and I owned him in short order.
Matron's Den--the worst of the worst, both in the minions and with Lilith herself. The place is full of those flying b*tches who incessantly cast Amp Damage and shoot those hurtful star thingies at you. They were a pain, but I just pumped the healing potions one after another and cut through them eventually. When I ran into Lilith, I quickly hoped into town and replaced my belt slots with all full rejuvination potions. Man, she bites hard, way worse than the other two mini ubers. Her poison damage is insane, and having antidote potions is basically pointless as she attacks so fast and relentlessly that a split second later, the poison has run you down. I treated her to a Battle Cry of course to weaken both her defense and damage, and it ended up being just barely enough. I almost died a couple of times, falling just under 100 life. The worst part is that she is poison immune, so I had to wait for each OW session to begin before I could make progress on killing her. Shortly enough in the duel, I ran out of full rejuvs and thought I was done for. At that point she was under about 25% of her health and she was bleeding from OW, so I took the chance to teleport back to town and stock up on all greater healing potions, since unfortunately you can't buy full rejuvs from the vendors. I ran back into the TP, crossing my fingers that I would survive with just the healing potions, and just before I ran out of those, I managed to deal the death blow to her. My heart was pounding through this whole battle, the only time that has ever happened to me when playing this game.
Now I have all 3 organs. However, I'm going to do Baal runs until I reach clvl 90 so I am in even better shape for the real Uber Tristram (and so I can wear the Standard of Heroes). It's just three more levels, but as you know at this point it takes forever to level, especially with having no Annihilus.
So, since I was able to defeat all three mini-ubers, do you think I have what it takes for Uber Tristram? Or are the 3 evil brothers really in a whole other league from the lessers?