A good prot warrior takes the least amount of damage of all the tanks (at least in Tomb)
Sco was completly off in his tomb tank rating video
I would say there are 3 tiers of tanks right now:
1. Druid, Monk, DK, Warrior - you can do any mythic boss on these without having much problems (except maybe KJ, but I didn't got there yet) lots of CDs, and can keep active mitigation (with correct talents for warrior) 100% or near 100%
2. DH - huge downside having wery few defensive CDs and can't keep up active mitigation 100%
3. Paladin - Low HP, Low dps and can't keep up AM 100% (Even white hits from bosses can drop you from 100% to 10%)
I'm pretty confident on my warrior right now, I'm almost allways taking half of the damage our bear does and do healing comparable to our healers
If you pick warrior and they say "lol reroll bear, warriors suck" they clearly haven't seen what a good prot warr can do