Honestly landing Cassiopea ult in a skirmish can feel like pure luck most times...
If you not hiding in a bush or an enemy is chasing you, landing the stun in a skirmish most times is pure luck. Even when the target is facing you, by the time you cast it, there's a good chance they will look away. Sometimes they don't even turn away intentionally, just moving around randomly or looking for another target and it completely throws off Cass ult.
And the thing is, Cass is so dependent on her ult in order to set up her Q/W. Otherwise she has to depends on her team CCing someone for her to follow up.
The point I'm making is, Cass can feel incredibly dependent on her team for a hyper carry. It doesn't ever feel like there is anything she can do on her own.
Just my thoughts after trying to master this champ for a few weeks.
we feel you