Well, if NRS ever hits that "button" they added and let you break throws while blocking, Jax's throw will be great because of the direction switching. It already does do 15%, too, but it's really hard to pull off... and yeah, the slide can't always punish gp cancels; Jax can essentially jump cancel his gp or cancel into another move.
I am not saying it's worthless, I am just saying you'll eat a lot of fast specials (a lot of them safe, too), for trying the gp cancel. Take for instance the matchup with Sub-Zero, since it's the one I somewhat know. If you start cancelling your gp with jump, Sub can just use ex freeze when he has meter. He's not going to lose no matter what you cancel into, so you're going to stop jumping against Sub-Zero (close range and far) eventually if you value your life bar. What can you cancel into that's going to force me into an error? There doesn't seem to be much unless there's something I am missing? If I am right, none of the guessing games after a gp cancel are really in Jax's favour so he's just putting himself in a bad situation by attempting it. That's why I don't feel Jax's baits are that strong off a gp cancel. I see plenty of people falling for ex dash punches and gp cancels because they don't know the matchup but once they know what they're doing, Jax seems limited to up close mix up pressure which cannot be sustained like a Johnny Cage frame trap or Kung Lao/Scorpion vortex.
Characters like Mileena, Sub-Zero, Smoke, Sonya (although she probably doesn't need it), can all approach Jax with d4 which is really annoying for Jax since his best stuff is duckable.
Anyway, I don't mean to bash Jax; I know 12gauge loves him, lol, I am just pointing out why I think he's not a top tier character. I think he's lower-mid or upper-low if that makes sense.
