[The_Paladin]

I voted for astral mostly for the versatility reasons stated earlier. Plus I know its a very high level spell but Strands of Arcane Power with arco I find to be very useful. If you are a way behind in gem income for whatever reason (or just want to jump ahead) that spell will help an amazing amount even if it does just find low-level sites typically. Also combine that with arcane nexus and wish if its still enabled and you will be rolling in the gems!

@Agrajag Yes air does cause stun / fatigue damage with its thunderstrike spell - making it quite useful indeed justifying its extra fatigue cost.