You can put a tank on 40k unbuffed by just running heroics. Raiding tanks can get easy to +45k HP.

Here is my tank as example: http://eu.wowarmory.com/character-sh...s&cn=Loladinus
By changing the gems it gets past 40k, but I am happy with some extra dodge and parry rather than more stamina. Fixing his belt and cloak (buying the frost emblems ones) he will be near 40k unbuffed with ease. I run only heroics and some raids from time to time, but not dedicated raider. Usually pass on loot for the other tanks to get it because their guilds would benefit more than me.

So I see absolutely nothing insane in 25 man raiding guild tank having +45k unbuffed... after all, heroics running tank can go to 40k with ease.