Something I do against a lot of Jin players (Though the really really good ones still find ways to eff me up) is just zone them with some of Ragna's longer range attacks. The most they can do at a distance is Ice blades or the Ice Car, both of which are easier to block than any of his close range moves. So if they're giving you a lot of trouble, try to stay just outside of their range and try to keep picking away at them with Ragna's C and D attacks ( I find 5C/2C and 5D both work good when doing this. Death Spike might also work in this case, having a large hitbox)
This is by no means full proof, and they'll probably realize what you're doing and try to get closer (Since it is a really predictable plan), but it's just an idea to try and get damage off them ( using drive attacks will help you regain some too ). I'm not too good with Ragna if I'm not all up in their face.