This used to be true, but they slowly buffed warriors, while slowly nerfing other tanks, the problem was it took them nearly 3/4 of the xp to do this, which really, really sucks, and lets hope they have all tanks reasonablly balanced at start of cata.
Remeber when we had a 50% devastate (or was it 70?), and only 6% hp scaling, and no shield wall glyph. They eventually nerfed dk cds, dk hp, paladin threat, paladin hp, and buffed warrior Hp scaling, awesome set bonuses, and huge dps/tps buffs (although still slightly behind, which shows how poor warrior tank dps used to be at one time).
"Gnoma Brasi sleeps withs the murlocs"