It would probably be fair for GM to rule that a Reliquarian casts their spells using WIS, but Rules as Written it needs WIS for mental focus and INT for spells, making it more MAD than other Occultist archetypes.
Was there ever a Word of Power from Paizo on whether this is intentional? I'm finally getting to play my Monk/Reliquarian in Return of the Runelords, so it basically decides whether or not I get to cast any spells...
I agree that, as written, it is Int-based divine casting.