That's a pretty good place to be in the HW rankings. Means he should get a shot at a HW belt and he certainly deserves one. 4th best is not an overestimate for this guy. Anything higher....yes.
Silver but should be Olympic gold medalist Second highest KO % of any champ other than Beterbiev Fought better competition in 15 fights than the Dosser has in 45 #3 HW in the world P4P top 10 Best chin in boxing
He'd be mismatched against Usyk. He would follow Usyk around pawing at him with his jabs that could be timed with a sundial, Usyk easily parrying and returning with lefts for 12 rounds. I'm thinking maybe 118-110 type scores.
Usyk beat Joyce in the amateurs just after Joyce won silver in the olympics but it wasn`t as one-sided as you`re suggesting here, Joyce is a non stop punching machine with a good jab and body attack, he`ll land more than AJ did and has better stamina.
Don't think I've seen anyone regard Joyce as a future world champ. So I'm not sure where the overestimation is. We know he has a good chin and good cardio. Good if not devastating power. Can quite easily see him beat Wilder and now probably Joshua. Maybe not Fury or Usyk but that doesn't make him bad just not top draw.
Then he'd be a champ in an era of beaten champions. Probably in the same tier as Wlad in his title reign. Good but not great. I've got Fury and Usyk heading towards great.