Bamboo RFs all have similar skills that involve gaining charges after the Skill is ready and needing to aim to spend all charges, dealing increasing Damage based on said charges.

This entire RF type has a few significant issues:

Bamboo RFs are generally not recommended, as simply using a standard self-buffer will yield usually better results. M21 is no exception.

M21 has rather underwhelming stats, with below average Damage and average values for everything else. As a result, her overall DPS ends up being relatively low even compared to RFs with similar Skills, as both her normal shots and her Aimed Shot Skill deal less damage than average. At maximum level, M21’s Aimed Shot Skill deals 5.0 times her base damage to the nearest target after a 1.5 second charge time. This skill is both rather ineffective at clearing mobs due to its long Initial Cooldown of 10 seconds and is also less efficient against bosses. Compared to the charged shot Skills of similar RFs, due to its low multiplier and M21’s low base Damage Aimed Shot simply can’t compete. Overall, M21 can generally be expected to underperform when compared to most other RFs, which is very unfortunate considering her rarity as a drop exclusive unit. Her low Damage hurts her overall performance too much for her to be considered except as a last resort, especially given that her Skill scales so poorly due to her subpar Damage stat.