It seems like you're getting ahead of yourself by going for heroics now - there's still a lot you can do first. You got the hard part out of the way - the PvP Gavel, but you're missing a lot of extra stats from gems/enchants on your gear.

A few items that would be an improvement:
- Extra defense trinket (+26 def from HFP Overlord quest, or +32 def from SL's Inciter) instead of Charm of Alacrity. 192 dodge is awesome, but it just doesn't help much in the long run for PvE in only 10s bursts.
- Get the libram from Sethekk Halls 1st boss. An easy kill for +47 Consecration damage. Easily the best tanking option until you can get the badges for +block rating for Holy Shield.
- Do the easy Shadow Labs quest for the tank bracers, or better yet, buy/make the Bracers of the Green Fortress - I just bought the plans on the AH for 600g on my server, but it took two weeks of checking before they were available. Run the SL first boss for the Platinum Shield of the Valorous.
- Buy/make the leg enchant - it's a lot of stam/agility you're missing out on. Agility also helps avoidance/armor.
- Buy/make the Delicate Eternium Band, do the BM quest for Andormu's Tear.
- Buy/make the Cloak of Eternity. If you know someone, the mats are relatively cheap - 6x Primal Earth + 6x Imbued Neth. Bolts.
- Keepers of time rep to Revered for Timewarden's Leggings.
- Scryer/Aldor rep to Revered for helm enchant - +dodge/defense is huge.
- Cenarion Expedition rep to Revered for tank neck.

Don't forget that boosting avoidance is always good, even if you don't have to worry about crushing blows. All those extra blocks, dodges, parries, and misses mean you're taking less damage. You'll still need plenty of heals, so don't worry about losing mana - swap in Seal of Wisdom when you need it. My pally is around 522 defense with ~59.5% avoidance before Holy Shield, and I haven't entered a heroic yet.
http://www.wowarmory.com/character-s...&n=Zandantilus