Alright, I'm new here so give me a sec to get used to the numeric pad little thing you guys have going.
My friend loves charging in, so a well timed 5D shuts most things down, I like to keep him frozen, so I tend to grab after a Frostbite, knowing he might (and very well likely) break out, I add in a couple 5a and/or a 5b before another grab, it's a matter of being unpredictable with it, if he screws up his grab release, free grab, however if he's expecting a late grab, then get him early to catch him off guard, but I digress since that whole tactic is universal, sorry.
aerial b seems to be better than any aerial Ragna has, except for his anti air, plus if I recall it combos into a 5d in the air.
Generally since Ragna lacks a projectile, Jin can camp and force an approach.
The Achilles Heel to this plan is that Ragna had really good approaches, but I personally find it suicidal to approach Ragna as Jin.
Oh yeah, Blizzard/Gale > Ragna.