Be a little bit careful trying to punish a whiffed GH, Ragna can still do the followup hit or not, and if you get hit with the follow-up your in for some real pain. But if you block the followup it's super easy to buffer a 720C.
Ragna is one of the few characters Tager can (sort of) AA (like axis said). From my experience 2A can beat Ragna's jA, jB, jC, but will lose to jD. 2C Works well for similar reasons. Also, keep in mind when pulling in Ragna from full screen with AC that he can ID through AC.