Before I start, I would like to say that all of this is my personal opinion.Decided to make a tier list for season 3 specificly.
S tier: Pathfinder, Wraith, Octane, Lifeline
A tier: Caustic, Gibraltar, Crypto, Mirage, Bangalore
B tier: Bloodhound, Wattson
Pathfinder: Even after the nerf, he still is a very good pick and provides a lot of mobility for everyone. I would say that he needs a small hitbox size increase (not smth to big)
Wraith: Very small. Very usefull. Don't know what to say about that final circle portal thingy. Making you taking damage in the storm is a bit drastic.
Octane: Underrated. The Launchpad could be buffed, but still very easy to learn and very powerfull.
Lifeline: Not much to say exept balanced.
Caustic: Balanced but could use a decrease on smoke blindness on teammates. Also World's Edge is not the best for him.
Gibraltar: Finally, good. Maybe a small hitbox decrease and he'll be S tier.
Crypto: Decrease the drone's noice and allow the EMP to damage ground shields. Then he'll be perfect.
Mirage: Underrated, a good buff for him it to make the decoy a.i. better, decrease the decoys of his ult and make them run.
Bangalore: No change needed, except for a decrease on her ult's cooldown
Bloodhound: The perfect buffs would be to make the wall hack last longer and allow him to use his tactical every 5 sec when his ult is activated.
Wattson: She's terrible on this map.