Jhin is either REALLY good, or REALLY bad. There is no in between. (At least from my experiences with Jhin.)
If possible I'd ask your ADC if he can play Lucian/Graves/Ezreal (Since they're the most broken, imo). If not, you'd need to work around Jhin (If you have a support that's compatible)
Jhin has no mobility and gets easily caught out. A high mobility enemy team fucks him.
They have a Zed? You have no ADC
They have a Yasuo? Better FF or open a lane, because Jhin can't do much.
Lulu might be a solid pick (Due to the speed up if there's a gank, and she has decent peels)
I've had some good times with Sona support for Jhin
Morgana is REALLY good with him
Nautilus (Another solid, amazing pick, assuming he makes it past ban phase)