Akali's Crescent Slash feels way too tacked-on. Any thoughts on updating/replacing it?

All it does is PbAOE damage scaling off her AD and AP, same as Katarina's Sinister Steel but pretty much inferior in almost every way. It deals physical instead of magic (which hurts her synergy regarding MPen) and costs energy by the boatload if you try and spam it. The fact that she can't keep moving while swinging it doesn't help at all.

In essence, I feel as if Akali would be better if her E skill was replaced by something new, but I have no idea what could be interesting enough to serve as a replacement. Alternatively, one could try to update the skill so it actually works better with her kit (i.e. change the damage to magic, allow her to use it while moving, etc).

Any thoughts?