VE Stacks for n% healing of the total of one priests damage.

ie 4 Shadow Priests Heal for 100% of One Priests Shadow Damage assume no resists / blown out by crits etc.
VT stacks for 20% of one priests damage when I have 4 Priests.

Paladin tanks with Mana, Priests Heal and Restore Mana through Damage. Works well.