Protection Paladins obviously can tank things, and I love to see them do it. A Protection Paladin tanking Illidan is awesome. Most raids, though, will look to the Warriors first. Not due to the inability to tank it, or even a gear hump. The lack of safety net on-demand survival tools is, in my opinion, the biggest issue with paladins as Main Tanks in a "post-2.3 world," as it was described to me yesterday afternoon.
Can Protection Paladins tank? Yes. Can Protection Paladins tank well? Yes, many people have proven this. Will they be looked to as the first choice in most situations? Unfortunately, no. That shouldn't stop you, though, and I never meant to imply that it should. I may have let my wry cynicism run away with me, and I apologize for letting it paint my words in a poorer light than I had planned. My stance remains that it probably will take some work for you to find a raid slot, but that doesn't mean you should not look. It also doesn't mean you'll be doing exclusively 'junk' jobs like trash packs. You have a hurdle to jump over, and you'll need to prove how capable you are to a raid.
As the folks over at Maintankadin pointed out, there are a few things I didn't take into consideration for my column yesterday that should be kept in mind. Thanks to the nature of Holy Shield(8 charges fully talented), a properly geared Protection Paladin, assuming there's no lag involved(whoop, got crushed between Holy Shield fading and going back up!), will most likely take fewer Crushing Blows. Against bosses that attack slowly, there isn't much of a difference between Warriors and Paladins, but bosses that attack very quickly? You'll really feel the difference.
Additionally, a Protection Paladin's health pool scales much higher than a Protection Warrior's does. Your on-demand abilities may be lacking, but at equal gear levels, you have a higher starting point, thanks to an extra 16% Stamina from talents.
There's other, smaller things, like fewer parries due to no special melee attacks to be parried, but I think all of that is better off being placed into my column from Saturday to be used as a proper reference for new raiding hybrids.
A friend of mine said something along the lines of, "In a competition between three people, getting the Bronze medal may be a prize, but it's still last place. Nobody likes to be in last place." To make the analogy needlessly complicated, it isn't a matter of first and last place. There's many categories in tanking. You get the Gold in some, you get the Bronze in others. Protection Paladins have one fewer Gold medal than the Warriors do. That doesn't make you a loser. It means you need to work a little harder to prove yourself.
I made some mistakes, but I'm totally willing to fix my inaccuracies if they're presented to me in a civil manner.
Oh, and before I go, I must warn everyone that applying to a raid as a Boomkin tank makes Baby Bornakk cry.