I don’t know if the invul > solemn defense part should be considered broken.

I think a lot of the time invul is good enough or they are removing your buff anyways. And it only works on her so if the enemy does have invul pierce, all your team mates are probably dead. This could have some uses like killing off dead supports though.

You also can’t have solemn defense and invul stacks at the same time on her(Edit:after testing, it looks like if the invul is from a CE such as Volumen Hydrargyrum, it will not be converted to solemn defense). Lastly, hit-based invuls/solemn defense can be problematic as they can block turn-based invuls.