The current state of 3v3 and 4v4 is absolutely abysmal RN which is likely why barely anyone plays them. 1v1 should come first in terms of balance but there are many things Blizzard could do without effecting balance at all or only minimally.
Problems:
- The Maps: The maps are some of the worst Ive ever seen in an RTS. The maps are either way too wide open which makes defense very difficult for certain races/playstyles or they are extremely cramped which forces most players into mass air. The one where 1 teammate spawns away from the other 2, which leads to a race to kill the lone player, and air space everywhere, which means almost everyone goes air, is one of the worst offenders.
- Protoss: Even despite the strength of Protoss in a 1v1 they kinda suck in team games. This is because the tech choices that Protoss needs to make vary the most from the other races (Zerg can go ling hydra into brood infestor and Terran can go Bio which are both comps that are good against almost everything). There is no comp that Protoss has that is good vs everything - the closest they have would be like mass stalker tempest colossus or something? Needless to say this is not a good comp to have compared with the options in the other races meaning you need to rely on teammates to counter the things your army does not which leads to the next problem. (check rankedftw race distribution in team games - there is a reason there are only about half as many Protoss players as the other 2 races).
- Race Balance: Imo the match making should balance races over MMR and also assign random players to races which balance out the races on each team (e.g. if the races are TTR vs TTZ the random player should be Z). This is because there are certain comps which are far better than others for example any comp involving a Zerg will force the enemy to patrol units everywhere to catch Nyduses. This would also help cut down on the absolutely broken match ups (e.g. PPP v TTT - good luck trying to survive mass reaper or a triple drop onto the same player while not screwing your eco by going full turtle).
- Zerg: Zerg is perhaps the biggest problem with team games RN. They by far have the most broken strats when it comes to 3v3/4v4. For example nydus worms allow a Zerg to teleport their whole ground army into your main, kill all your tech, then as soon as you come back or counter attack their side of the map they can get out right away. In 1v1 its mildly balanced because there will be barely anything to defend a counterattack (team games have teammates) and the maps are smaller so there are less places to Nydus and its faster to retreat to deal with the problem. Nyduses can also drop their whole army onto a teammates to 2v1 a player before their teammates can help. Swarm Host + Nydus is another ridiculous strategy in team games, in 1v1 the counter would be just to send a drop/warp prism to their side of the map and force them to use locusts defensively but of course that’s not required in team games since they have teammates to protect them so they can snipe your bases with little consequence. And finally the last problem with Zerg is not being able to build on an ally’s creep. Creep is considered neutral but the rules can be changed to make it so that as long as there are no enemy creep tumors within a certain range of a creep tile you can build on it.
TLDR: The maps suck, they need to have just the right number of choke points but not such extreme chokes/too many air spaces that everyone goes air. Nydus and Nydus + Swarm Host effectively ruin the meta - there is already alot of complaints about it in 1v1 so Blizzard should definitely look into adjusting it. You should be able to build on creep if there are no enemy tumors in range. Race balance is more important than MMR balance (eg TTT v TZZ should be rebalanced to TTZ v TTZ).