Power Infusion now stacks with timewarp/bloodlust.

What does power infusion not stack with?

Power Infusion Does NOT Stack with Heroism

Things such as Heroism/Bloodlust are considered External, and therefor DO NOT stack with PI. You can, of course, still cast PI during a Heroism/BL, but the only benefit received will be the mana reduction – quite the waste of a powerful spell.

Does Arcane Power and Power Infusion stack?

Arcane Power does not stack with Power Infusion. If Arcane Power is already active, a priest casting Power Infusion will receive an error message "A more powerful spell is already active." If Power Infusion is already active on the mage, activating Arcane Power will override it.