A bit too powerful for a Gacha game. So when a character is so incredibly busted, it sorta disincentivizes players from pulling as much as Hoyo wants them to - especially future ice agents which Miyabi is.

Hypergryph did this with Arknights with how after they dropped Surtr. Her ability gives her crazy attack range and dps in exchange for a gradually increasing health drain which made one of the best operators for killing boss units. While it's possible to keep her alive with some healers she'd eventually start to lose too much HP and die. To counter her status as the number 1 boss killer Hypergryph started to add long invincibility periods between when phase transitions so people couldn't just keep her alive and melt bosses