(So I have not played the game myself, so the following is just what i got from watching the game)
From what i've seen the new hero, Soldier 76, looks like a semi mobile beefy-ish damage dealer. he has a lot of characteristics that you get from other typical FPS games. But in my opinion his ult (Q) does not fit his kit well and is kinda useless.
First of all, it makes him from a kinda medium skill cap hero to easy mode hero because of its lock on affect. this makes it nice for new fps players but for skilled players his ult does basically nothing at all, cuz ya know, they know how to aim.
What I would do to change it (just a quick idea) is the following:
turn it into a grenade, a small but like tracers but this has range. It could work in a way where its damage and size of the AOE is not too good, but if you kill someone with the ability it puts it back at like say 80% charge, so you can potentially use it in quick succession. I think this fits in much better because while you're running and gunning around the map, you can throw out you're grenade get a kill, shoot a few people and keep the cycle going. giving this hero a sustain in fights.
So yeah, have a nice day and tell me, what do you guys think about my idea?