Well, you have a point...
I agree that this isn't a perfect game, but IMO it's INCREDIBLY well made.
3 turn wins should happen sometimes, they are a consequence of luck in card games. If you somehow make 3 turn wins impossible, and 4 turn wins very rare, you'll inevitably nerf rushes OR slow down the game, maybe too much.
I don't say winning in 3 turns is OK, but it's too improbable, and generally any good CC can counter it, so maybe it's not that bad.
You may have had a bad draw (it's common, specially for ImmoNovaRushes and PSNbows) and your opponent, a REALLY good one (or you might have miscounted the turns*).
There is some stuff that can't be changed... You can't kill rushes/stalls/denials/other deck archetypes, and they are pretty balanced right now. It's true that Immolation and Supernova are a bit OP, but it's just a bit, since they can still lose to other stuff (specially Black Holes).
*I know you can see them in the losing screen, but maybe you haven't done that and exagerated a bit, or maybe it was YOUR 3th turn, and the opponent was in its 4th, when he won and didn't let you reach your 4th.