As I stated in the first post I would put it at 2 it would be situationally better than mage (1 more dmg, but I lose health if I attack a minion).
Sometimes better than hunter (I can attack minions), but I can't go face if he has taunt.
I know they won't do it at this point. And true, this expansion put DH on top again (thanks multistrike, Pufferfist and Naga package), but you can't deny DH is the class (behind warlock) that relies the most on his HP
The hero power to 2 would solve lot of issues and make the class less overpowered.
As someone else stated, at 1 DH never has floating mana. Also tempo wise, they can immediately answer 1hp minions on turn 1 without having to use the coin.
There are many cards that benefit from DH attacking: the 2drop that summons minions on 3, Pufferfist + hero power on 4... Delay it by a turn and suddenly DH is less threatening, without necessarily being a garbage class.
Also, it would be perfectly in line with other hero powers. Not strictly better or worse than any other