Rune of Power has been reworked to cast at your location when you use one of either Combustion, Arcane Power, or Icy Veins, depending on your spec.
Developers’ notes: This change is aimed to help with the cast time and GCD utilization at the beginning of an encounter, while remaining viable in your opener as a high burst window.
This is from the mage class changes today as seen on Wowhead.
Still doesn’t solve the issue of AP doing essentially nothing for 1,5s while still being dispellable and several GCDs in the exact order spent buffing up. AND desynchronising AP from other CDs is just bad. 15s duration/90s cd was the way to go with other CDs on 40-45s cooldown.