Karin does not have hard combos compared to the rest of the cast though. She has a few non optimal combos that have some tricky shit going on but her BnBs are simple(I'd say her swaggy stuff isn't even that hard since the games execution is just that easy but whatever.
character difficulty isn't all about combo difficulty though. Matchup wise Karin has a better time than Ken and tool wise she blows him out of the water. As for kens hit confirms being easy, they might be compared to other games. However, in sfv they're harder than pretty much everyone else's. Karin doesn't even have to confirm, she can just end in shoulder instead of tenko, or just end in any of her non negative buttons(all of them).
Edit: also, shame on you for saying kens st MK is the second best whiff punish normal in the game. Karin, Chun, and Necalli at least have better ones.