(Remember this is just my opinion open for discussion so dont just downvote to hell if you not agree or because my grammar (not native speaker 😅) , comment your idea if you think is better)
First only legend that needs nerf is Gibraltar because now he is little to op, left him faster revival then other legends because you should have more options then lifeline for healers (just need to be slower then lifelines) , but he must louse 25 hit points from his shield and add longer coldown on arm shield
Lifeline must be good enough to be option in professional play, she is only real healer so she needs buff, so people have option to choose her over Gibby.
Buff her health drone to heal faster, full heal in 5,6 sec like big health item, (more people use in same time it it's slower) and when she revives player let her shield stay second longer up to give him time for getaway
Bloodhound tactical is usually useless, everyone can agree, when you scan you just give away your position, so he needs to be changed. Change it to be like throwing knife that scan people like in Titanfall, rest can stay same
Mirage my boy, love him but almost nobody fall on his decois , so he needs buff, just give them little health so they can survive few shoots, one or two, and just for fun when mirage revive teammates let just him be invisible and make some funny animation of revive
Cripto now is good, I don't play him much, maybe he should stun teammates also because in pro play not stunning teammates is too Op but not shure, He only needs in my opinion ability do destroy Watson ult and fence whit his if he can't do it already.
Bangalore is perfect how it is now
Octain he needs buff, to not be so fucking loud when stim himself and run and not to glow so much for tactical. For his Ult he need jump pad that propel him forward not up, like in his lore when he blow granade under him, to be real speed demon, he should be faster then Pathfinder going forward and maybe just for fun also, when revive teammate he should stim him to go faster.
Caustic is good how he is, He is situacional legend, his poison smoke maybe should not slowdown his team but definitely should mess whit wiew, and he should have abilitie to trow traps faster so he can use them like cover in middle of fighting, he is second biggest legend.
Watson is must have in professional play so don't think she needs buff, maybe just small buff of restoring 25% of shield shield when revives a down teammate to be more useful in normal play,
Pathfinder is one of best legends only because his tactical so no need to be changed, if you buff other legends people will not mind his superior mobility that much, like now.
And for last best legend in game Wrath, her get of jail free card tactical is just nerfed so if nerf is shown to be to much should be lessened to 30 sec from 35, if not then nothing needs to be changed. She have smallest hit box and best ultimate in game so she will be always top legend