This card is way, way too powerful. Even "Draw a card. Rebound" for two mana is pretty good.

I think the UU keeps it pretty fair. It's on the higher power side, but you are overstating it compared to a cube environment.

As far as I'm concerned, Think Twice is a tier one card. This is a sorcery, but it still seems rather strong, roughly giving you the flashback on Think Twice without paying for it, plus two bonus loots.

I admit, it's hard to guage power cubes, though. It could certainly be fair for your cube. In normal Magic, though, I'd say the card would be a fine common if you removed the Rebound.

It's true that in high power Cubes, most card draw is a little too slow, and it should be about half a mana or a full mana cheaper. "draw a card, rebound" is a bit worse than Divination, and it only matters in late game. Even if you topdeck it, you still get one card before you wait. Drawing two and discarding one for two as a sorcery is fine, if a bit on the weak side. Doing so again for free is more than twice as strong. And remember that draw spells are always stronger if the rest of the cards are stronger.

I think people think it's important that individual cards are much better in a Cube, but it's really just a matter of setting up the environment. If you don't have things like Wall of Omens or cheap removal to slow down aggro, and expect draw spells to be good, then, yes, you need this. But if you do, you can get away with anything from Divination to Fact or Fiction. Test this, and you'll see it's pretty unfair for its costs.