You stay back until his counter strike ends, then hit him and kite as much as possible. If you're playing Vayne, you can easily use your stealth to kite him to death, and if he ever gets close to killing you, you can condemn him away, regardless if it stuns or not.
Jax is pretty snowbally though, that's for sure.
@Diana
My problem with not taking Zhonya's ASAP is because Diana is such a good initiator, I can QRE in and that slows everybody and puts them close to me, which puts me in a dangerous situation, so I tend to zhonya's right after to avoid being exploded and making them shift targets to someone else while I gather my bearings and explode their carry as soon as the stasis ends.