There should be a reduction in resource income in the higher game modes to bring the pacing back to similar to the 1v1 modes.
The way Dawn of War 2 handled it was by reducing the amount of resources each point gave by the game mode. In 1v1 a requisition point was +15 and matured to +30, in 3v3 it was +5 and matured to +10 in 3v3. Power income was similarly divided by the number of players. (Requisition was basically manpower, the reason you got way less in team games was because you didn't have to build as many power generators)
I'm baffled that this system isn't in the game, to be honest. Especially since they go out of their way to ensure that there's always 8/10 strat points, 2 muni and 2 fuel points on almost every map. Capping the map faster due to more players also increases early game income significantly.
Caches are also a less risky investment due to the larger map size. (Although I'd imagine that a player who made a point of hunting cache's would be a huge boon to their team.)
I always kind of considered the entire purpose of 3v3/4v4 to let people live out their fantasies of large tank battles though. 2v2 I don't really notice much of a difference outside of the natural benefits of larger maps.