I hope Kayne's S.A form would have more benefits on his skills.
Just a list here. Passive: damage is a bit low. The mitigation really is a letdown and has not much a visible effect compared to Raast. I have heard building crit or tri is good on him using this passive. But both are way too expensive for junglers.
Q: Not reliable enough to get to the backline. It sort of needs a bit more range ,or to be more fluid in motion. R: As for a assassin ultimate it is very lackluster. Very LOW damage, and there is the risk that the ulted person will run back to his allies and your team backing off. It is very HIGH risk to use it as a squishy assassin.
I wish these points will be addressed in the future for S.A Kayne as I love playing it.