The game itself takes no issue at levels. People are people and monsters are monsters. Experience and levels is *mostly* for the player perspective. That's why the Pitax guy (I think?) and his retinue is so high level he could have cleared books 1-2-3 by himself with like a squire and a warden.
I've adressed this viewpoint in my very first post in this thread. Disconnecting the player perspective from the setting perspective destroys verissimilitude. I have yet to see a player I'd like to retain in my group, who won't bothered by the fact that his/her character exists in a virtual landscape, where enemies scale depending on what adventure PCs are in. Those who aren't into immersion still will be annoyed upon realisation that their hard-earned levels earn them only increase in paperwork, as their tacticool plans and power acquisition schemes are meaningless in a world without at least aprroximately defined opposition benchmarks.
That's why Irovetti having Fighters and Bards of level 6 as standard mooks, even though the same adventure path assumes that by same level 6 PCs are supposed to be semi-independent lords already. Irovetti isn't even a powerful sovereign who can be expected to have famous heroes under his command - he's a petty bandit king, who earned his position by gambling!
Thankfully, very vew things that actually happen in the first 4 parts - and as I realised recently after carefully reading part 5, there as well - actually require antagonists to be high level. With a handful of exceptions (Vordakai, Armag's tomb, maybe Hargulka), everything else until Nyrissa's hit the stage is E6 material, and often works much better when played at low levels. For example, an assumption that PCs might possibly be forced to run from a bunch of mooks reinforced by some melee brutes, as in the initial encounter of part 4, is much more reasonable if the party about level 5, than if it is level 10.
So I'm currently planning for PCs to deal with the whole Drelev and Pitax plots soon after the Stag King and probably in parrallel with the Hargulka's problem. Using antagonists stablocks from early adventures, of course.
"We have sent the best of their troops on the other missions - and that damned Oleg bloke is being a nuisance and asking for help again! What have we got left? Not a lot, all the decent volunteers have gone to Drelev and Varnhold. the mercenaries are off playing with the barbarians. So all we have left are a few low level guardsmen. We need all the decent fighters in case Surtova gets excited ....I know - lets see if we can get some volunteers to go help Oleg. If we offer them some sort of Charter to clean the place up so they feel important and tell them we will pay them handsomely IF they succeed ..."
Well, that might work as an explanation too, if one is generally fine with Golarion's overall scheme of level scaling (I hate it, but this is a matter of personal taste).