Currently there is a pretty severe lack of mechanical accuracy and tooltip information on how passives function. I believe it is stemming from changes made in 1.4 though they were unlisted or possibly unintentional, and certainly by now with new issues popping up with the most recent patches are now definitely unintentional stemming from changes to functionality made that should be reverted.
Either intentionally or unintentionally some passive abilities now do not proc items, when previously they used to like Morigesh passive previously had full proc functionality. I say some because this is extremely inconsistent and tooltips and common sense do not line up on what actually happens with how inconsistent this mechanic is applied. Let me give you a quick (but not exhaustive there are so many to test and I guarantee there are more inconsistencies among the cast) list of abilities to illustrate how bad this is.
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Aurora passive procs every item, Noxia, Megacosm, Tainted, Dreambinder etc. This is also you might note infinitely refreshing procs as long as you keep hitting the person, so its a pretty extreme example of a passive being able to proc everything.
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Morigesh passive procs nothing whatsoever.
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Gideon passive procs no items like Megacosm, but does proc the mana regen augment on ability damage.
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Belica AUTO ATTACK passive augment does not proc items but does proc the mana regen augment on ability casts.
If this was intentional, I think the change should be reverted and if certain characters need reciprocal nerfs, like Mori (though she wasn't broken before with full procs), do so. But as it stands now the current solution is poor with horrible readability for players where items and augments will basically randomly work or not depending on the character you play with no tooltip or information in game giving you the knowledge of what will and won't work.