I really like how they distinguis visualy Eldrich Blasts for every subclas!
I wonder if they even alterned animation to feel less necrotic and more ... related to that subclass.
Also, feel free to corect me but the main problem with Wyll as a Hexblade is that they basicaly have pact with their weapons, wich dont goes from Fiends ... and we allready know he have pact with Mizora.
But on the other hand, there is enough other "exceptions" to oversigh this one aswell.

I like him as Fiend Pack...he gets fireball.
He has Eldritch Spear for that extra reach and two blasts now.
...and the super-imp concept is pretty fun...an invisible AOE striker for all damage occasions, with nice resists and poison immunity.
A nice extra: because wyll's spell slots auto upgrade, he casts his invisibility as an AoE (nothing to do with Fiend). Great for say., running past the Mask people to get Ethel, if you want to try to save them. Many uses for group invisibility...battle setup, yada, yada, and WOW, didn't think of that yet.