In order to offset the increased risk and make using melee weapons more desirable and worth using, they should be worth 55 or 60 points instead of 50. High risk, high reward- especially when there are multiple zombies around. Perhaps combos with melee weapons stack, with the first kill worth 50 pts, the second worth 55, the third worth 60, the forth with 65, and the rest in an ongoing chain worth 70
In my opinion, they’re already quite balanced by having a massive damage output (as in, can take down the boss in only a couple of hits). It’s probably one of the reasons Survivor is one of the most popular classes used.