So far best combo for me and my friends is Invis/jetpack and he goes Armour lockdown,

We have played 9 games today and won 8, but the 9th, im pretty sure it was standby because our screens went black, and then other team were like 8 kills up.

Any tips for doubles?

Stay within sight or 2-3 second walking distance of each other.
Team shot everything.
Control power weapons

just went against a team that camped with invis and power weapons entire game was fucking nasty.

still beat em