Guize on Skullcrusher has come up with what I think is a very interesting solution to the problem of endgame survivability for Rogues (we'll put PvP aside for a second and just talk about PvE for now). Currently, as players have said before, Rogues are a liability in most endgame raids-- yes, they can dish out damage, but considering how many endgame bosses pour out AoE, Rogues often end up to be more of a drain on the healers than anything else. I'm sure Cloak of Shadows has helped that a little bit (I haven't got too much experience with it yet, as my Rogue is only 61), but the fact is that while tanks can take it, Rogues take a beating more than any other class (ok, maybe healers take a worse beating, but that's only in a bad party).
Enter Guize's suggestion of a 31-point Combat talent that allows Rogues to wear mail armor (alternately, to avoid having to add tons of new agility mail gear, he says it could just be a talent that bumps up armor from items). That would let PvE Rogues not be so squishy when asked to be right up there on the front lines of melee, and it would help out healers a whole lot, especially on the 25 and even 40 man instances.
Now, in terms of PvP, I have to admit it seems a little unbalanced at first, considering that rogues are basically killing machines. But remember, too, that magic ignores armor-- Warlocks and Priests will still be able to DoT and fear just as much as they did before (and Cloak of Shadows is more of a problem for them anyway, and it's already in the game). There is, of course, the problem that it's really hard to be stealthy when all that mail armor would be clinking around, but if you want to finally give rogues a chance against the endgame AoE bosses, giving them the option to wear mail would definitely do it.