Well there is surprisingly good teamwork in public games at hard setting, but I can’t do it on insane difficulty probably due to lack of communication and knowing eachothers playstyle. My playstyle for example is:
(MEDIC) Flamethrower + Medical gun + Health pack
I basically torch every alien once then let them burn or let my teammates finish them off, other then that I spend time healing teammates or getting rid of infestations.
Gotta say though, the medical gun is awesome, flamethrower is maybe a bit overpowered as it ‘stuns’ aliens and also kills them over time (the basic alien that is)