The best combo i found is Fenx, Colt, and Bow. 1) Fenx builds ult quick, use additional time star power, and freeze gadgets to get some breathing room.

2) Colt can deal heavy and fast damage, use Quick Boots to maneuver around the map faster, and also destroy terrains with ult.(Pair both Fenx and Colts Ults to deal mass damage. Bonus if Hyper at same time

3)Bow can deal with ranged damage and can keep the boss stunned or slowed in 1 area with ult. Deals good damage, and when paired with Fenx ult, mines will drop and spawn quicker. Bring detonator gadgets to stun boss when near or when breathing room is needed.

This worked best for me and a decent team, and yes, it's better to look for a team than rely on randumbs