Not really. Especially if you set the swarm hosts to attack from different directions. Even with 8 Colossus they have to be micro'd back and forth a lot to even make a dent in units that are basically free. The units lost disparity in many games I've seen is just too much to call it balanced. Void rays are a good counter, Battleships would be too, but it's kinda unfair to have to go deep tier 3 to counter and mid game unit.