I actually really like demon Wyll, he looks very warlock-ish. He looks very whatever beforehand, like just your random noble swordsman. The transformation gives him a lot of flavor. I know he will lose power from Mizora, but hopefully when he goes to Avernus with Karlach to kill her, or beforehand, he finds away to absorb demonic powers for himself or cheat her out of them so he can turn them against her in revenge and keep being a blade of avernus as he claims.
How else is he going to be useful? His entire run in our campaign has been as a warlock, being a vanilla rapier duelist just feels bad when you compared him to some juiced up vampire spawn or a githyanki with a silver sword or a hell engine powered barbarian.
