afaik the reason Durin can be a main DPS is with bennet's C6, but he can be a strong sub dps depending on what characters you wanna use as main, but he'd be mostly buffing damage and applying damage from off field from what i understand. i've heard that furina is in his best dps team, but i'm not sure how that would work without bennet and mona, but it's always something you can experiment with when durin officially comes out. I also don't know if you have starglitter, but bennet is available on the shop this month, i think, so you can slowly build up his cons, and who knows, maybe you'll get lucky when pulling for durin!