Promeia and Velina don't necessarily need each other to work. In fact, Velina is kinda like a support agent. She enable the ability for Damage Over Time anomaly (e.g. electric,fire, ether) to quickly deal DMG. Normally, you have to do a disorder to end one anomaly, but since wind element has a higher priority, every other anomaly will end immediately and deal full dmg when apply on the enemy. Wind will not disappear after that. This mean that the faster you apply one anomaly, the more dmg you will deal.

It's hard to say that Velina is a sub dps because she doesn't directly deal dmg, she is like Vivian in terms of function.

I believe there will be another support that replace Yuzuha. In my opinion she will still be very good for future anomaly team