Top 3 Hardcore Uber Builds

1. Concentrate Barbarian

The top pick goes to the Concentrate Barbarian. Barbarians have high health and defense with Battle Orders, Concentrate, and Shout. Concentrate is the safest build for Ubers in hardcore followed by Frenzy Barbs and Wolf Barbs.

Recommendation: Concentrate Barbarian

Stats: Enough Strength for gear, 136 Dexterity (to use a Grief Phase Blade), all remaining points in Vitality, no Energy

Build:

20 Concentrate

20 Battle Orders

20 Shout

20 Sword Mastery

1 Battle Command

1 Berserk

Enough in Natural Resistance with charms to reach 120 Lightning Resistance over cap for Mephisto's Conviction Aura

All remaining points in Bash as a Concentrate synergy

Weapon: Grief Phase Blade

Weapon Switch: 2 +3 to Warcries weapons

Shield: Stormshield

Amulet: Angelics Amulet (you will need high attack rating against the level 110 Ubers)

Rings: Angelics Ring and Raven Frost

Helm: Guillaume's Face (high crushing blow and deadly strike)

Armor: Chains of Honor Runeword (65 All Resistances to over stack resistances against Uber Mephisto)

Budget Armor: Smoke Runeword (50 All Resistances)

Belt: Thundergod's Vigor (for Uber Mephistos Lightning attack)

Gloves: Dracul's Grasp (for Life Tap curse which is needed to stay alive)

Feet: Gore Riders (for Crushing Blow and Deadly Strike)

Charms: Resistance health charms (especially lightning resistance) and attack rating health charms (preferably with max damage)

Charms 2: Barbarian Torch and Annihilus

2. Fury Druid

Fury Druids have very high health thanks to Shapeshifting, Lycanthropy, and Oak Sage, and are fairly inexpensive to build. Fury Druids benefit greatly from an up'd Ribcracker which is the best Fury Weapon for boss fights. The next best build for Ubers is a Fire Claw Druids which can complete Ubers with Grief in hardcore once they have the Infinity Runeword on their mercenary to break Uber Diablo's fire immunity.

Recommendation: Fury Druid

Stats: Enough Strength for gear, 0 Dexterity (attack rating will come from Metalgrid Amulet and one Raven Frosts), all the rest in Vitality, 0 Energy

Build:

20 Werewolf

20 Lycanthropy

20 Fury

20 Feral Rage

All remaining points in Oak Sage

Weapon: Up'd Ribracker (the best weapon crushing blow weapon for Fury Druid vs bosses)

Weapon Switch: Call to Arms and Spirit Monarch

Amulet: Metal Grid (you will need high all resistance without a shield and attack rating against the level 110 Ubers)

Rings: Raven Frost and a high all resistance rare or crafted ring

Helm: Up'd Jalal's Mane

Armor: Chains of Honor Runeword (65 All Resistances to over stack resistances against Uber Mephisto)

Budget Armor: Smoke Runeword (50 All Resistances)

Belt: Thundergod's Vigor (for Uber Mephistos Lightning attack)

Gloves: Dracul's Grasp (for Life Tap curse which is needed to stay alive)

Feet: Gore Riders (for Crushing Blow and Deadly Strike)

Charms: Shapeshifting Skill Grand Charms with health and resistance charms with health (especially lightning resistance)

Charms 2: Druid Torch and Annihilus

3. Smite Paladin

Smite Paladins can complete Ubers in hardcore without top tier gear but, I wouldn't recommend them for Uber Tristram solo on hardcore. The fight can still be very dangerous for a Smite Paladin until you have an Exile Runeword shield to proc Life Tap at the beginning of the fight.

Recommendation: Smite Paladin

Stats: Enough strength for gear, 136 Dexterity (to use a Grief Phase Blade), all other points in Vitality, 0 Energy

Build:

20 Smite

20 Fanaticism

20 Holy Shield

20 Lightning Resistance for 10 to Maximum Lightning Resistance

All remaining Points in Resist Fire for Maximum Fire Resistance

Weapon: Grief Phase Blade

Weapon Switch: Call to Arms and Spirit Monarch

Shield: Exile Runeword (you will want a fast source of Life Tap for Ubers)

Budget Shield: Stormshield

Amulet: Maras Amulet (+2 skills and high all resistances)

Budget Amulet: Metal Grid for 35 All Resistance if you are on a budget (attack rating is not needed for Smite)

Rings: Raven Frost and a high all resistance rare or crafted ring

Helm: Kira's Guardian (for up to 85 all resistance with an Um rune)

Armor: Duress Runeword for all resistance and crushing blow when using Kira's Guardian for resistances

Belt: Thundergod's Vigor (for Uber Mephistos Lightning attack)

Gloves: Dracul's Grasp (for a second Life Tap curse)

Feet: Up'd Goblin Toe (deadly strike on Gore Riders doesn't work with Smite and Goblin Toe has higher crushing blow)

Charms: Health charms with high resistances

Charms 2: Paladin Torch and Annihilus

Tips:

1. Crushing Blow will be your primary source of damage with melee build against the very high health Uber bosses so make sure to equip enough Crushing Blow on your equipment for the fights.

2. Uber Mephisto has a Conviction Aura that lowers your resistances by 120 and summons mages throughout the fight that deal elemental damage which makes over stacked resistances very helpful. The most dangerous aspect of Mephisto, however, is his lightning attacks so you should gear up to about 120 lightning resistance over the cap to safely fight Uber Mephisto.

3. Uber Baal can drain mana very quickly so make sure you have enough mana potions in your belt when you face him. Insight is also very helpful to have on your mercenary for its mana regeneration on several builds for Uber Baal.

4. Uber Diablo can be dangerous to Life Tap with a wand on Smite Paladins because of his bone cage ability so natural sources of Life Tap are preferred over using a wand.

5. Most enemies in the Uber Tristram fights are immune to elements which makes physical builds more effective for the fights. Physical builds also have access to the Life Tap curse from Dracul's Grasp to keep your character alive for the heavy damage that is dealt by the Uber bosses.