Zerg has no early game no, its just defend defend defend defend attack win.
I see more and more players are figuring out how strong the vipers are and Zerg has more options now late game, but ofc early game is a bit harder.
I see more and more zergs going for the Zergling/hydra/viper for then to transition to Swarmhosts as a stepping stone to get to a final unit ultras or broodlords. Strong zerg players like DRG, Stephano Nestea looks unstoppable with this new HoTS unit mixture, vipers so important versus a meching player mainly because of this blinding cloud.
And I agree with Medivac being strong, good Terran players attacking absolutely everywhere at once.
But all in all, is really HoTS that imbalanced now? I don't really think so. Each race is strong at different stages of the game, that's the way the game was designed in the first place.