I think he is fine character wise, you can see some cracks and hints in the facade he is building up, I'd love to deepdive into his story and rescue him from the devil and whatever deal he has going on.
What is really holding him back though? You have only 3 slots left for other party members, and you have Gale, amazing wizard, solid choice, you have Shadowheart and all the new cleric spells, smashing, you got Lae'zel who can solo an entire boss just with her thousands of hard hitting attacks, even Asterion with his bonus sneak attacks is an absolute killer.
Wyll as a warlock doesn't quite measure up to these guys, at least that's how I feel, and if you never pick him, it's hard to get invested in his story. If his class was more enticing and explosive, say something more melee focused that'd be fitting, like a swashbuckler for example, you'd be more open to him, for sure!
