>>539215798
You'd design maps in such a way that if your teamwork is good, you pick your positions well and you correctly prioritize targets, your team guns down everything around. If you do not have these things down you will get flanked or blindsided by a powerful enemy or isolated and killed.
Melee would be for conserving ammo against enemies of strength or numbers that do not necessitate forcing them into a disadvantageous environment or buying time if your position is broken.
Basically, figure out how to do space hulk but not exclusively in a bunch of claustrophobic corridors and you're not terminators.