I don't understand the focus on warrior tanking ability between specs. Druids and Paladins have the same problem. Holy/Ret pallies and Balance/Resto druids tank just about as well(poorly) as an Arms/Fury warrior. What's the big deal?
If tanking is your job, you spec Prot, Prot, or Feral. If it's not, you spec something else, and can fill in on trash or something if you're needed to. Seems balanced to me.
it's not really that simple though, a warrior will simply not get a group as a heroic tank in a pug, or shouldn't even try to, if they aren't protection. a paladin can easily get a group as holy or protection (i've run several heroics with a ret pally as well), a druid as feral or resto or even boomkin. but a pug will ask/see you arent prot, and simply find someone else. this is a change that every class and player should be welcoming because it will increase the amount of viable tanks on your server for pugs, and increase the amount of warriors willing to run a heroic in their pvp spec without a paladin healer.