1) Put all important AA on timetraining if you dont have them. Decisive Strikes x5, Resolve, Void of Madness should all be trained before you think of joining a HM.
2) Build. Offtank or maintank? As off tank with low gear, go with a Desecration build with Armor, Goad, Improved Def stance and Cunning Deflection. As main tank you will not likely hold agro without dying until you get more dps (taps) or more gear (survivability). You will find the threshold while playing. You should always aim at having 50,1% armor mitigation at minimum while tanking physical encounters.
3) Gear. Helm, Hands, Chest, Legs, Rings and Weapons should *always* have the "Critical Rating" stat on them. Even if it means it is not heavy or full plate armor. Starting out, you should get Helm and Gloves of the Warmaster (crafted trader items). Energetic Bands or Dreamers Keepsake rings. Blue Iron Hammer and Talisman of Power or a **** shield and do KK until Essence of Courage and Entropy talisman drop. Chest and Legs, go with class epics from T1/2 until you farm enough rares / get lucky and get the good ones. Tamarin Tiger chest and Last Legion Battlements legs are the "best" Khitai items for DT in Chest and Legs slot.
4) Rare Trophy farming. A lot of it. I don't think I am overestimating when I say I have farmed between 2500-3000 Rare Trophies on Shaxtina.
Actually not. You need to meet mitigation tresholds for Khitai 6-men instances. You most likely won't in blues. T2 chest and legs will boost mitigation so far up, you can wear magic damage / wisdom stuff and compensate for lost damage from blues and still be over 50,1% mitigation.
FYI: At Palace you want to break line of sight on the spell cast by the healer. He will however run over to you and smack you with a physical hit before you can break line of sight again. Protection gear is a complete waste here, unless you plan on letting him cast spells on you while you dps boss. But you need at least 45-50% protection to not die and nice dps to be able to do that.