Perhaps making the AoE indicator 3D would help? Adding a definitive border or making it look cyndrillical or spherical would be cool. But then people would complain about that. The way I see it, you only have two options SE.

1- AoE effects are rainbows and have fireworks blasting out of them. (Can simultaneously show tribute to the LGBT players)
2- Enemies could have the common courtesy to say "Excuse me, but I am about to attack in a fan-shaped area directly in front of me, might try to avoid it best you can good sir."