No one. It would have just been a much better placed pass that should have been caught but was dropped. No one said Hartline shouldn't have caught it either way or that Tannehill underthrowing it just a bit is what caused Hartline to drop it. Personally, as I said before, the ball should have been caught. It was certainly not one of Tannehill's worst throws of the game, either, but it is exactly the kind of throw that is driving people crazy. I know even the best QBs in the league miss on deep balls, but they also hit them with far more regularity than Tannehill has as well.
Hartline had like two steps on the guy and there was no safety even remotely close until just as the ball was landing. On shots like that, the receiver should not have to slow up to catch it. It should be an easy walk-in touchdown. Bad on Hartline for dropping what was still a very catchable ball. But also bad on Tannehill for poor ball placement. Nitpicky as the one pass may be in a vacuum, it still remains true, and when combined with all the other awfully placed throws (including several very short passes) so far, it paints a bit of a disconcerting picture. Not yet in permanent ink, but definitely getting there.
MOST of the deep passes that are completed by other QBs involve adjustment by the receiver. They are caught and no one gives them a second thought.
As others have said, if Hartline, Wallace, and Sims make the routine catches, we are talking about how much the deep ball has improved.