No Lifeline Nerf? Then Nerf The Yellow Backpack
If you don't want to nerf one of the strongest legends in the game then nerf one of the things that makes her broken. The Yellow Backpack. Make it a one time use item like the self revive shield. So after one revive it turns purple. You gave her a free hand revive in the game that doesn't need to be channeled. That alone breaks the flow of a fight as it is. Gibraltar needs to channel the revive AND he can be pushed by just running into his dome. Lifeline is reviving while shooting at you so she's holding pressure to keep you back. If you don't want to fix that aspect of her then revert her revive back to season 1. Channeled with a shield in front. That way you don't break the flow of a fight because she has to channel it. Ever since her change to a free handed revive (not on cooldown btw) she's been busted and the fact that you go and buff every other aspect of her kit to "compensate" her revive "nerf" is a joke in of itself.
So either change the yellow backpack
OR
Revert her back to release
Give her the fast revive I don't care as long as she has to channel it.
OR
Change the yellow backpack even further and make it even more dynamic and make the yellow backpack quick revive and remove all fast revive in the game period. Yellow backpack no longer gives bonuses on revives but instead anyone can utilize it to its full potential now.