Hook was broken. If you ask me, there's times where it still is, but now in the reverse form.
It was changed because he wouldn't have LoS on you, but you could throw his hook and since it counted as a projectile it would hook your character above their frame and pull you to him. Now, there's times where I've been hooked and it breaks because the payload moves in front of him right as it connects, or a street sign breaks his LoS. It doesn't happen often, but still see it time to time.
The issue is that Hog's hook was broken and that is why it got changed.
Mercy's Rez is not. It might not seem fair at times, but she is pretty easy to take out now. A lot of it comes down to awareness. If you kill Rein in front of your whole team, and you watch Mercy swoop in and start a Rez while watching your team ignore her, that's the people playing the game, not Mercy.
She only truely seems broken against teams that don't push.