Nope, since in a day we're going to be on our way to 80 and that cements the TBC era content as trivial
I've been looking around at a bunch of friends' armory's and almost none of them have 490 def. They tank t4 content just fine.
Does having 490 even matter anymore?
490 Def was always the goal for being uncrittable. There're two ways you can be uncrittable, Defense and Resilience, and the reduction is pretty much independant of all the other factors.
Against a lvl 73 mob (i.e. raid boss), you have a 5.6% base chance to be critically hit. 490 Defense (+140 from base at 70) covers that span, though if they have resilience that will close the gap as well, and actually will go farther per point (though you lose the avoidance value that comes with it, especially as a Warrior/Pally). If you had 475 Defense though, you only have a 0.6% chance to be crit, so you won't see it popping up all the time, in the past it was more essential because in a long enough window that spike of damage would toast you. These days it's far less an issue because if you're running with remotely geared folks in t4 the bosses will die in 60 seconds or so.
Like Xav said, though, since that becomes moot in 48 hours, I'd highly recommend hitting 540 defense when you get to 80 if you intend to tank. The fights will take longer, and the game will feel closer to the old challenge and balance, so you'll be happy not to be critted.