I use all 3 pieces of the Iceguard set (Helm, Legs, Chest). Then I use the epic Frost Resist ring, and the blue Frost Resist neck. Both pieces are made with Jewelcrafting which I conveniently have at max skill level.
I use my Justicar Shoulders and Gloves. What I'm after here is the 2 piece set bonus. I need good threat on the Hydross fight, especially as the Frost tank. The time from the pull to the first transition is "free" dps. I don't want my DPS team holding back due to threat issues.
I use the Merciless Gladiador Gavel and the Merciless Gladiator's Shield Wall. The benefit here is to get Resilience. The Resilience on these "pvp" pieces helps make up for the lack of defense I have in this gear. I think it's around 463 defense, and 43 Resilience.
The rest of my gear is filled in with pretty "standard" tanking gear. I try to get pieces with Defense, so I use Crimson Girlde of the Indomitable over the Girdle of the Protector or Belt of the Guardian, and the Scrab of Displacement over Moroes Pocketwatch.
I use the Wristguards of Determination because of their high avoidance.
The only gear I enchant for resist is gear that is only used in this set like Iceguard stuff. The rest of the gear gets standard tanking enchants.