j.B is a huge pain, my only suggestion is to attempt to IB that and the following move (if it's a jump-in they'll do a 5b, else it's the usual j.C).
Anyway, I realized that if Jin is doing a blockstring if you can't IB atleast barrier guarding will work since his best move up close is 5b, once he is out of range for that he'll either:
- crossup/jump-in j.B
- 5C
- 5D
- 236A
If he does 5C or 5D it's good news for you, as others suggested 2b is really effective whenever they're trying to poke with one of the two moves.
If it's a 236A, crawl and punish on reaction for a CH
Problem is if he tries the crossup j.B. As you said that move has a ridiculous hitbox (and ridiculous priority as well), best bet is to attempt again a IB->6a but it really requires some yomi/reflexes. In any case, most of the Jins will usually go for the poke if they've been pushed far. Just don't let them close in, their 5b is a real bother because it'll always allow to start their frame trap game.
Anyway, lately I've been having more success against Jin players because they tend to abuse the same things and get easily predictable. So far I only had real trouble against Jin who played nice mind games and resets every time they managed to get in and start their offense.