Now, to be honest, it's not like this is against Alleria characterization.
Alleria entire characterization in WC2 was her art and 5-6 lines when selected (the art does explain the ''click emote'' Keep your gaze focused..) and beyond that, well there was the novelization where (surprise) she was an Elf that really did not liked the Horde. The bulk of the characterization beyond that was made by her sisters.
But while it's not exactly improbable for a Windrunner to make a pact with dark powers to avenge hersellf, where exactly her foray in voids magics is coming from ?