It's not card advantage because of the discard, but a double Regrowth for 3 mana seems OK, specially since it's on a better color. I mean, getting Ancestral + Time Walk or even Shattering Spree + an instant seems pretty ok to me. I mean, even things like Preordain + counter/Gush is pretty OK, specially if you discard lands after Gushing. Pity it doesn't cost 1R, but we can't have everything.

The card advantage depends on what you're discarding. Squee, reanimation or welder targets.

Hey look it's a more different Recoup / Past in Flames.

I don't like it as much as either of its predecessors!