The problem is, frankly speaking, I think fixing mercy is beyond the devs ability, rez as a regular skill is unbalencible, ether its viable to pull it off, in which case it becomes OP by default, or you nerf it to the point where its useless, there is no in-between.
Many mercy players have figured this out from day one, why do you think it used to only be us who shouted for reverts? Now the rest of the playerbase has finally caught up.