30% damage nerf. The developers even said it was supposed to weaken his hook combo. I guess going from "killing" to "not killing" is a form of weakening.
Its not just his effectivess, his whole feels is gone. He fires and reloads so fast now you don't need to think about the timing of your shots. That's just... not roadhog. Plus he generates so much ult for the enemy, he's the only character in the game where its better to be AFK than play Roadhog in his current state.
Edit: To be clear, Roadhog's self heal is not intended to tank in the conventional sense. You want to funnel damage into the other tanks because damage taken on a barrier doesn't build enemy ults and doesn't require any time from your healers. But you don't want to funnel damage onto Roadhog because Roadhog's ult is weak and every point of damage he takes builds his bad ult in exchange for an enemy's good ult (or wastes a healer's time). The way that Roadhog tanks is with intimidation. You don't want to get near Roadhog, you don't want to go in a building with Roadhog, or turn a blind corner into him. Roadhog's ult is part of this, because even 3v1 you want don't want to rush Roadhog carelessly. His entire character runs on fear, on threats rather than execution. Yeah getting that pick early wins fights, but more importantly the THREAT of the pick changes how the enemy team has to play all the time. Its not like Roadhog is particularly stealthy, most times against good players he won't actually get a pick anyway. But now there's no fear. All day I've seen Mercys dive right on top of gold gun Roadhogs because like what's he going to do? If he hooks he stuns himself and by the time he's done with the combo he'll be dead and the Mercy won't be.