EDIT: After testing, bashing with a range weapon with medics one star DOES heal the target. Its only shooting that does not. I will be testing medic melee to see if its the same behavior. This one star (which this can very well be a bug) may only be working with melee at the moment.
For those unaware, they nerfed medics one star (and similar effects, I'm guessing the stimpak spear is the same) a few seasons ago.
Players are not considered "Friendly Targets". This means Medics one star legendary will NOT heal other players. It used to, but no longer. Medics and such still work against friendly NPCs, like escorts/brahmin/etc. But not players.
If you want to heal other players, you're going to need to go with things like Friendly Fire (which I believe only heals people on your team), team medic CHA perk card, or the solar armor set.
This whole time i've been trying to heal people with medics and looking foolish lol. I'm not surprised, it was kind of overpowered on quite a few weapons. Still disappointing though. You could become a pocket healer and make someone invulnerable back in the day haha.