It's a terrible spell. It costs 3 mana and 4 cards.
Oh, wait, he put Squadron Hawk text on it, yeah that's not gonna happen.
Yeah, obviously that particular design is busted, but it's just a proof-of-concept.
Legendaries are unique that's how their significance is measured. Without the legendary rule legendary doesn't mean anything.
Epic captured that essence I don't know what else could.
But legends are only partially unique. If you exile my Thalia, I can immediately play another one. They're unique while in-play, but not otherwise, even in terms of
effects. Instants and sorceries are never in play, so there's no reason to try and bring that rules baggage along when talking about non-permanents.
One issue, though, is that Legendary creatures are typically more powerful for their mana costs because of the legendary downside. In limited, you're usually just getting extra power at no cost, because you don't have multiples anyway. The issue with the legendary spells above is that, you're paying extra in limited for a weak effect. In constructed 8 damage for 3 mana is nuts, but often in limited it would be RRR mana for a shock, which is pretty awful. It also creates those corner cases where multiple copies are opened and they wheel, so someone ends up with a busted deck by getting 3 or 4 of them.
