That said,I don't play mages(other than AW) on difficulties above Perilous.Maybe when I reach Promotion lord status that will change 
If you played my Ele build, you wouldn't have this issue. You don't need promotes to do it, due to it being primarily CC with self rez and burst fire dps, with barrier mixed in. Sure, fire immune enemies would take one damage. Those same fire immune enemies are CC'ed by FStorm KD + WoF Panic.
Also super fun with the Fire Pact Belt, and a Fire Staff if you don't use hakkon's
Crazy damage (pact belt + chaotic focus + fire mine, or even basic attacks), Self Revive with Persistent spells + HoK, constant mana/health from death siphon, barrier, guardian spirit, paralyze (static charge), knockdown, panic...
Allies with single target DPS take care of any fire immune enemies around, as they now have barrier from you, and the enemy is CC'ed so its harder to die.
What's not to like? It totally does not depend on promotes at all to work (as CC is unaffected by gear, and barrier is barely affected), but scales up with gear improvements quite well.
AW's actually one of the worse canidates for higher difficulties despite how highly others rate it. It may be easy to use and gets quick returns with fade shield, but its potential is much less too. Less damage, less cc, etc. All it has going for it is dps based barrier on self. and all the other team based barriers are better.