Let's face it, multi-coop is brutal
For every player, there are 6(!) bots, spread over three different teams. This is different from normal coop, where for every player, there are 2 bots.
This means that multi-coop is practically 3 times harder. Depending on the gamemode, the bots attacking each other makes it easier (ctf/etc.) or harder (deathmatch).
So, here is my proposal:
For every player, add 1 bot to each team in multi.
This means that for every player, there will be 3 bots, which is still more than normal coop, but only 1.5 times that, not 3 times.