Its weird for sure. There's one particular group of people I can see it working well against; genuine rebels against the Orthodoxy, i.e people who believe they are still loyal to the emperor but who disagree with the interpretation of the will of the emperor the faction of the Inquisition doing the fighting at that moment uses.
Exceptionally good at infighting I think.
I mean, its the Inquisition. Their art being backassward in terms of who it works against is kind of on brand for them.
Bundling my response to these since it's kinda the same: the Inquisition being prone to infighting is absolutely part of the flavor of what makes the Inquisition what it is, in the setting. But I enjoy that much more when it's epiphenomenal and the product of human nature when given a role with these parameters, rather than built into their Path itself at the conceptual level.
Basically, I like 40k, but I like it much more when it stays on the right side of the grimdark/grimderp divide. And the premise of the Inquisition as a Path being basically the cultivation of Divine Infighting Arts at the active expense of being effective in their assigned role is just... way too on the nose for me. I like it more when they've got every tool they need to be excellent at what they're
supposed to do, and then
still descend into being a pit of vipers.
On a lighter note, I'm really hoping that this setting features cultivatorks, who cultivate the sacred essence of WAAAGH! You could have it laid out like:
Grot Realm - Da runtz. Krumpin' 'em is good fer a laff. Dey can carry yer stuff, too.
Boyz Realm - Ta reach da Boyz Realm, ya gots to krump 'fore ya get krumped. Dead simple, but a bunch of gits still can't figure it. Daft, innit? Now dat ya ain't a grot no more, ya can get proppa stuck in!
Nob Realm - Da Nob Realm is fer dem Boyz wot found the alignment of their spirits wuz wiv either MORE DAKKA or MORE CHOPPA.
Boss Realm - Da Boss is an ork wot knows the answer to askin' MORE DAKKA or MORE CHOPPA is always YES. All orks can benefit from da Waaagh energy, but da Boss is an ork wot can
lead it.
Big Boss Realm - Da path of da ork is da path of conquest. Ya wants ta be the
Big Boss? Yer gonna need to beat down uvver Bosses 'til da Waaagh itself feels it.
Warboss Realm - Da Big Boss Realm is fer orks wot can conquer der peers. Da Warboss Realm is fer orks wot can conquer da
world. Yer gonna need to build an' lead a whole Waaagh of yer own ta reach this one.
[...]
Gork/Mork Realm - REACH
HEVVEN
THRU
KRUMPIN'