World of Warcraft Patch 2.4

[Mordekhuul]

Also prot warriors are just as worthless as prot paladins when they aren't tanking. Druids are unique in their ability to switch between dps and tanking.

That is true only in fights where the prot warrior must wear his tanking gear. Fury geared prot warriors can do DPS about on par with cats at tier 5+ gear levels, I understand.

This is why in my ZA runs, I generally tank mobs like Akil'zon, since adding an extra healer would be meaningless, but adding a prot warrior in DPS gear adds a good 600+ dps for us.