There is plenty to incentivize them, medics can reach top of the scoreboard without getting a single kill.
Many players run by because you aren't in a safe place, you are 2-13 and spending time healing won't suddenly make you go 30-3, or they are the top fragger and actually playing objs and kills. No one is obligated to immediately stop what they are doing and rez you when you go down.
Regardless, what needs to happen is other classes need a worse way to heal themselves than medic. Ie, they can only heal themselves to 90 HP, while stationary. This alleviates the primary issue of why medic is so popular, sine it's the only class that can self heal, while still keeping medic as extremely important, since it's the only class that can heal itself/others to 100 HP, as well as having 20 bandages and faster animations, and can self heal while remaining mobile. This opens up assault, engineer, and support to being more fragging out classes, while medic could still do it well, it wouldn't be the best simply because those other class bonuses are already insanely good.
Once that's done, see how things are, then buff/nerf accordingly. For example, maybe medics lose C4 and get C2, which would be more of a breaching charge and much weaker against players. Or maybe medics don't have access to ARs, and instead get DMRs, or lose access to SMGs.
But there's no point in looking at any form of nerfs until the other classes are actually playable and fun, and imo, that will not happen unless they get a (more limited) form of self sustain, because being unable to reset yourself just makes them unplayable. Having only a single "fair" fight isn't fun, especially when there's aim punch and armor mechanics on top of that. There needs to be some form of resetting, but auto HP regen does not fit in with battlebits pace, so that's out.