I know you're not a huge fan of Tannehill, but certainly even you can see the difference between him and the worst QB in the NFL (yes, including several backups), at the moment. Miller is 100% of that offense, followed distantly by Blue. And he's being used as a power back, which is a terrible fit, obviously. And yet he's still putting up the 5th best numbers against some top defenses. Yes, he's very good.
Osweiler isn't even close to being as bad as Bortles, and I think Osweiler sucks.