Warriors have it hard from 60 to 70. Paladins can level Prot just fine (some even say it's the prefered level spec) and the same can be said for Druids that level Feral. They can both level fast and when asked to tank, fill said role without changing their spec. Arms or Fury is the prefered level spec for Warriors but we miss out on important tanking abilities like Last Stand, Imp Shield Block and Devastate which makes it more difficult to hold aggro or survive the beating.
Last night while trying to form a PuG for Ramparts I came across 3 Warriors, myself included, who were either Arms or Fury and none were interested in tanking or respeccing Protection.
I finally just said screw it and strapped on my shield, brought in a Rogue, Hunter and a Mage friend but had the hardest time finding the OTHER important part of the group.. a healer.
I guess healers are in the same boat that Warriors are. I don't say tanks due to the above statement. Shaman, Paladins, Priests and Druids do not level Resto/Holy. If anything, you'll always be stuck with one of these classes in a healing set of gear much like a Warrior wearing more tank-friendly gear. Sometimes it works but sometimes it doesn't.
My Druid is Balance but I heal just fine. My Warrior is Fury but I tank just fine. It just takes a little more effort than normal to make ends meet.
Last night I tanked Ramparts after spending 45 minutes looking for someone to heal. We had little to no problems at all and no one died. Not too shabby for my first tanking job since SFK lol.