Looking at Arians' career it's hard to determine if he had success because of his scheme or because of his QB. He's looked great with Andrew Luck, Big Ben, and Carson Palmer but not so much with Tim Couch, Kelly Holcomb, and Blaine Gabbert.
Luck and Big Ben have been great with multiple OCs. Carson Palmer was putting up good numbers in a Bob Bratkowski offense.
There's no doubt that Arians knows offense but the "QB Whisperer" deal is a little overblown. If you're whispering to good QBs then you're going to have success. If you're whispering to bums you'll be looking for another job soon.