I agree with ulsh, your gears fine for heroics, but running without any CC will be pushing your healer to the max, at 16k armor, 15k health i still find my commendation procing (under 35% health) on the MS mobs, so use CC liberally until you get a few more pieces of badge gear.
Just a note: when you aren't gemming purely for stamina, always enchant for defense where you can, since it will allow you to swap out a defense gem to throw in a 12 stamina gem in a socket, and keep the same defense and pick up more stam. Look at reenchanting you chest, bracer and gloves (vindicator's armor kit) for defense, and then maybe swapping gems around for more stamina
As for HMGT - its pretty easy to tank to be honest. Theres always a shortage of tanks for it (at least on my server), since although it has one of the best tanking trinkets in the game, it has no other tanking gear, so most tanks run it for the trinket and then never set foot there again, expect perhaps to help out friends. That said, even though its a difficult instance, most of the difficulty in trash is simply caused by a lack of CC, and the bosses arent really a gear check:
Boss I - easy as hell
Boss II - all arcane damage, mostly a healer check since theres A LOT of party damage, the boss doesnt hit especially hard
Boss III - Untankable, throw on heal set and keep ur healer up, throw around HoJ, and BoP a clothie when they need it
Boss IV - Easy to tank, only tanking the fireballs, and you have bubble for if your dps cant keep up with the "enrage" timer pyroblast.
That said, when going, make sure you get at least 2 CC, to make the 3rd boss bearable if you get a nasty combination, 3 would be ideal, as there are also some rather large trash packs with lots of casters which hurt a fair bit.
