You will now need 540 defense at level 80 to be uncrittable. This may not seem like alot, but defense rating has changed and it takes alot more to get where you need to go. Plan on gemming for defense and enchanting to defense until you hit that magic number. You dont want to go into a heroic and start getting critted for 8-9 thousand.
This should be the first priority for all of you warrior tanks out there. Effective health will come in time. Make sure that your healer isnt running out of mana on every pull.