Brick is hands down the best tank in BL1, even better at it than Lilith with a defender com (though she is no slouch). Why Brick?
From Skills alone, you have:
+40% Shield Capacity
+60% Maximum Health
+60% Damage Resistance on Kill (7 secs)
+40% Explosive Damage Resistance (deep in Blaster Tree, stacks additively with previous entry)
+150% Revive Health
+100% FFYL time
Regenerate 75% of Shield capacity over 5 seconds when it is depleted for the first time since a full-recharge.
During Berserk, you regenerate 3% of maximum health per second (after buffs to maximum are accounted for).
Berserk lasts 18 seconds by default, but skills can increase that to 27 before com is considered.
Brick can achieve the highest shield capacity in the game, while also having more health than any of the other VHs in that game, and he regenerated 120% of that shield in 5 seconds upon its depletion (so unless they do enough damage in those 5 seconds, it fully recharges every time it goes down).