In 1v1, a variation on this strat is to go all-in - send your queen after you spawn larvae, and then when the second 4 come out send most of your drones. With 7 roaches + drones + queen, it doesn't matter if he gets out the Immortal, or infact what he goes for. Only thing I've seen is a hard cannon wall, which then commits him to a single base Void rush - which is easily countered.
So yes, this strategy is very unbalanced. Played 22 games tonight, 7 losses. 2 of those losses where on 2v2. Last 10 games I played? 9 wins, 1 loss.
I hope Blizzard fixes this soon :( it's going to make Terran and Toss very susceptable early game.
But I do agree that ranking for larger teams is poor - for example, I'm 3v3 Platinum, and I'm definitely out of my league - I think I ranked their as a result of being lucky in terms of getting good team mates.
1. Against Toss it's almost always a win, especially if you go all in (attack using queen and half your drones). Unless he's got a closed wall with cannons, he can't stop you. In my experience, no-one does this in just about any league.
2. Against Terran, it's very succesful, if not quite as succesful as against Protoss. If they put up a bunker with marauders, or they micro 2 or 3 marauders behind a wall, you need to fall back. But in general, it works amazingly.
3. Against Zerg it works very well, as long as they don't six pool - if they do six pool and you haven't scouted it then you are in trouble. But in general, it worked well.
Bottom line? Although it seems like it's similar to the traditional zerg rushes, it's actually a very impressive rush. I would say that well executed it's got a 90% success rate on maps with short to medium rush distances. So definitely give it a try :)