One downside for event girls however, is that they usually deal low damage to crystal because they have weak passive skill. Burst cannon can be game changer because you can't rely on Nazuna's whim if she insist on using pea shooter.
That's true. Take a look at Saffron, she was really medicore pre-bloom. Once bloomed however, she turned into one of the most broken unit in the game with unusually good combination of skill.