It seems my Domain doesn't scale with Inquisitor levels but character level.
Law Domain is at level 14 and I'm Level 10 Sacred Huntsmaster and 4 Hellknight.
I dunno if its because of Impossible Domain : Animal, or if its just how it is.
If it's bugged then its probably bugged on a per-ability basis. I haven't noticed that with other domains but then you have to looks closely if you're only slightly multiclassed.
It seems to be that way with Law Domain, at least.
I have 2 uses of Staff of Order.
You get one use at level 8 and an extra use every 4 levels afterwards in the class that gave you that domain.
If it only counted Sacred Huntmaster I would only have 1 use as I'm level 11.
However, as I'm level 14 total I have 2 uses.
If that's how it is with all domains then I'm fine with it; it makes multiclassing and prestige classes more viable.