Well, my old setup for WarRock was, have a sniper, two medics, and the rest assaults.
One medic would cover the assault, the sniper would be hidden, and taking out whatever he sees.
The other medic rushes, the rest of the assaults, if there are any, would rush with the other medic, though taking a different route.
Splitting up and watching your own back makes it slightly harder for you, but harder for them as well.
I find sticking together quite, well. Dumb.
Seeing as a single nade will take you all out if thrown correctly.
I never use chat, seeing as it can make everything worse, you'll get type killed.
I use Vent, and hotkey a button to enable my mic.
Sticking together makes you and your teammates a easy target, simply distracted by fire from an assault, and then finished by a sniper.
Distraction is also a unused tactic in clan matches.