A case can be even made that the Orks are the only actually sane species in WH40k (In an insane universe, the only true insanity is insisting on sanity. Ergo, the Orks, who just enjoy fighting for the sake of fighting, are the only people with a sane approach to warfare in the year 40000)

So, yeah. Clearly Orks are the true protagonists in the 40k universe.