+1 to Bodh's stats.
Though if you're offtanking or only tanking the first 4 bosses (up to but excluding Curator) 11k HP is WAY more than enough if you're uncrushable, which is 102.4 combined Miss, Block, Dodge, and Parry with Holy Shield up.
Gruul and Magtheridon take significant upgrades.
I would expect a tank to have a minimum of 14k unbuffed HP (and if you're doing it right all tanks will have a crack at a "Boss"). Definitly uncrushable, 490 defense, and to perform well they should have a ~200 Spell Damage weapon, which will then get buffed with Oil and the Major Spellpower enchant. More spell damage wouldn't hurt, though there's nothing god aweful wrong if you only have a ~120 Spell Damage weapon still. Magtheridon is basically infinite threat for a Paladin tank (demon) but Maulgar and Gruul give you a taste of tanking living bosses.
Mana longevity is a bigger issue for Gruul/Magtheridon healers. Another % or 2 crit would be gravy, but 100-120 mp5 while casting I'm sure should suffice considering there's probably 6 other healers.