Five mana for a 2/4 that makes one token and grows itself next turn is the floor, and that floor alone clears the maindeck bar in a medium-speed format. The realistic case is why this is the defining bomb of the set. TMT commons sit at 2/2 and
2/3 rates with one to two removal spells per color, which means boards in the four-to-seven-turn window routinely stall at three or four creatures a side. Resolving her on that board makes four or five bodies, then the attack trigger puts a counter on every one of them, including the freshly-minted 2/2s. No common in the format profitably blocks the result.
She is P1P1 in any white seat and a splash worth bending a second color toward. RW Equipment and WB go-wide are her homes, and they want her for different reasons. WB treats her as the engine that converts a stalled board into lethal reach; RW treats her as the finisher that turns a curve that has run out of gas back into damage, with Bespoke Bō on a counter-pumped body closing fast.
The honest read on her fragility is narrower than it looks. Killing her in response to the enters trigger does shrink the token count: X is counted on resolution, so if she is gone she does not count herself, and you get one fewer 2/2 (zero if she was alone). But once she has attacked, removal is too late. Grounded for Life can kill her after attackers are declared, but the counter trigger is already on the stack and resolves anyway. The window that actually matters is killing her before she swings, and the format's medium removal density does not guarantee anyone has it in time.

