How to build enough aggro if you're the second tank?

If they want you to tank VR it is in your and their best interest for you to be the first tank. It's not a small issue. When they see that they can crank up dps far beyond the other two tanks and then have everyone dump aggro when they're finally catching up to you (after a few knock-backs) they'll realize the benefit.

If they won't let you tank first, do the following (actually, do these either way if you can):
1) Buff spell damage as much as you can. Use a Flask of Blinding Light, Superior Wizard Oil and spell damage food.
2) Get a shadow priest in your group if you can.
3) Get a ret pally in your group if you can.
4) Judge Crusader.
5) Use SoV (if you're alliance) but make sure you apply with with wings up.
6) Slam mana pots every time the cooldown is up. The ones you can only use in Tempest Keep (Nethergon something-or-other) stack to 15 and are cheaper than super mana pots on my realm.
7) DO NOT waste mana on Holy Shield when you are not the tank.
DO NOT wear any arcane resist gear. You need to take the damage from pounding to get heals to feed your mana pool.
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I stack as much +dmg as I can while being uncrushable and over 13k buffed HP. (~500-600 +dmg)

I judge crusader (effectively 700-800+Dmg)
Seal, pop wings and let fly with all the holy damage I can. When Hit ~50% mana, I downrank cons and keep going.

I use rank 2 or 3 holy shield unless he's on me, thank max rank. Destruction pots or mana pots everytime you can is a big bonus.
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