So you've dinged level 85, and you're on the cusp of the elusive endgame. Now come the first steps of your progression as counted in ilevels rather than actual levels. For a fresh tankadin hitting heroics for the first time, you're going to find it a more difficult jump than back in Wrath when all you needed to tank heroics successfully was some moxie, whatever random quest gear you accumulated along the way to 80, and 535 defense. (I'm building this up, but it's really not that bad.)
In any case, in this article I'm not going to specifically say "get pieces X, Y, and Z," because tanking is about tailoring your gear to a current situation. So while one piece might be amazing for two kinds of scenarios, it could be subpar for others, and I'd like to stress keeping a wide range of gear available so you can mix and match as needed. As such, I'm going to use this space to tell you what pieces are available where and recommend stats you'll profit from -- in essense, give you a fishing rod rather than the fish.