sated devour and jax

{quoted}

No his W and ult stack will NOT proc phantom hit... they are on--hit effects but they are exeptions

Exceptions The following "on-hit effects" are classified as abilities and will trigger spell effects, rather than on-hit effects. It is unknown of this behaviour is an oversight or intentional as they are visually identical to the on-hit effects of other champions. The triggering attack will still trigger on-hit effects.

more or less they are on-hit effects(looks wise) but are treated as spell effects.

Source: http://leagueoflegends.wikia.com/wiki/On-hit_effect

jax ult passive and his W are onhit effects....

Grandmaster's Might is a self-buff ability that passive grants Jax an on-hit effect on all his basic attacks. Applies spell effects as a single target ability. Hextech Revolver item.png Spell vamp is fully applied. Rylai's Crystal Scepter item.png Rylai's Crystal Scepter will apply a 35% slow. The triggering attack will apply other on-hit effects and can critically strike as normal.

going off of this it would be a bug if it didnt work on him. either that or riot swept some stuff under the rug and didnt tell us.