@Meddler. I don't think Cass was the right champion to give grounded too
I had a Cass flash ult me and I actually had the reflex to turn around and not get stunned. She drops miasma right on me though so then I can't use any escape spells and her jungler dove me too. And that happens at any point. A champion that builds Rylais should not also be able to straight up deny any spell chance for escape especially if you manage to outplay the ult. Especially considering the fact that is huge and comes out instantly. Maybe it was just jungle synergy but I definitely feel like her W has a larger scale impact and influence than her ult even because there is not outplaying the cass w you just walk away while getting slowed and chunked for tons of damage
TLDR Grounded allows Cass to get away with being outplayed on ult which is something that players that outplay/manage to dodge the flash ult shouldn't be getting screwed over anyways with. PLus the miasma seems insane when I see it in pro play.