Playing at a level that's over/under where a player was drafted & just playing a role on a team are 2 different things.
Walton played worse than a 4th Rounder - You had him as a 3rd/4th rounder after the combine, and had hyped him as one of the best RB's in the country. I thought he'd be a 6th after the combine, after thinking wouldn't be drafted at all before his Junior year. I always said he was an undrafted free agent type talent, and no way he was a Top 10 RB in the draft. Now he's out of the league in under a year.
Dorsett has played well below a 1st Rounder - If the Patriots valued him, they would've signed him to more than a 1 year "prove it" contract this offseason. They signed 3 other WR's to 1 year deals. They'll probably draft a WR early, maybe 2, with their 12 draft picks. It would be great to see Dorsett and Berrios playing a role for the Patriots, but it's far from a given.
Thomas has not played like a 3rd rounder (yet) - Yes, the GM is expecting more than the nothing he gave them last year. But he'll be behind a good example of an overachieving Miami guy - Olivier Vernon. He's gonna have to fight to be a rotational player.
I totally understand if people don't remember high picks that didn't work out if their careers weren't very memorable. But the "Miami guys are always undervalued" as a blanket statement just isn't true. Plenty of examples where it is, plenty of examples where it isn't.