Blitz seems balanced, but unhealthy...
I mean, its like Katarina or Riven. Feast or famine. If they're winning, they snowball to fuck. If they're losing, they're essentially useless.
Blitz, if he loses, basically wards and is a meat shield(one that's probably really behind and still squishy). But if he wins, him and his teammate can just freeze lane by tower, and sit inbetween the minions and their enemy. If they come in, they get pulled and killed. Generally with that tactic you can even win against a jungler gank, the only way to win against that tactic is probably to get a 4 to 5-man gank.
Its not that Blitz is unbalanced but... he's really unhealthy for the game. He's the kind of guy that makes people just want to quit. Not saying I know what to do about it, but if Riot has any ideas, I think they should at least try them.