Pretty sure Paizo follows the general guideline, if you stat it, they will kill it. Gods, Archdevils, the Immortals Rakshasha are not stated because of their unfathomable power and leaving it up to the GM/DM.
Do a search right now for "tarrasque" and see how many threads are devoted to killing it. Even if the stats say 'lol no' there will still be threads labeled "level 4 party taking out the Tarrasque"
Anyway, I would assume that monk would be a must for Irori. Qinggong monk might be an interesting archetype since it would allow a more mystical feel. Jokingly, I would say that he should have infinite Ki (or infinite for out purposes) so he could just spam every ki power there is and just smack everyone around.
He definitely has monk lvls, with infinite Ki...
BUT,
Because the gods are so powerful, I try to imagine them not as single-class 20lvl characters.
Instead each and everyone of them are 'super' mystictheurges with 20lvls of cleric 20lvls of wizard, and 20(yes 20) lvls of mystictheurge, with all spells prepared and the ability to cast them all with metamagic spontaneously.
with that as a starting point, I then think... what would separate Mystictheurge (Irori) with Mystictheurge (other god)?
Probably another 20lvls of monk atleast, and a higher-than-the-average-god Wisdom score however high a god wisdom score is... because they are not really stat-ed, and for the above reason.
Eh, not really Oracle.
It's more like they have super-duper epic levels and stats in their "class" and all of them have a "racial" ability to cast Miracle at-will.
So Irori is like a level, say, 300 Monk with infinite wisdom (hey, he's achieved enlightenment after all) and therefore infinite Ki and AC.