I know that an observer must have more than 81 hp in order for a computer to blind it but i believe this isnt possible on a map with 8 players thus leaving no room for a computer. Do you guys know a way to make this happen? thx in advance

You'll need to rely on the human players to blind things. IIRC P9-11's Medics don't do it.

I don't know of a way to make your players cooperate though.