Ideal WarTank gear:
#1 Mastery / (Dodge/Parry)
#2 Dodge/Parry with one reforged to mastery.
Parry should be kept roughly 2.5% higher than dodge, that's approxmiately the point where returns from HtL are equal to the diminishing returns from keeping parry higher than dodge (without HtL, dodge should = parry due to the same diminishing returns)
Gems are typically:
Yellow = Mastery
Blue = Green Mastery/Stamina
Red = Parry/Mastery
If you can swap a (Dodge/parry) / (hit/exp) item for either a Mastery/(Dodge/parry) or Dodge/Parry it is best to do that.
In heroic raids, threat stats have more value, but sub heroic raids, you should be able to maintain your threat lead in the first 15 seconds without much issue if your rotation is good, so you don't really need threat stats. I'm running .64% hit and 3 exp and threat, even in heroics, is a non-issue (as long as DPS doesn't ride my ass into the fight).
Don't swap down typically though if your gear has master/dodge/parry and something else on it unless the lower level has a boatload of mastery. And even then, it may not be an upgrade.