Fantasy Flight Games Only War is a rpg for the Imperial Guard of Warhammer 40k.
We attempted this game as written, and then after house ruling. But core issues with scaling, advancement, and overpowered traits result in a broken campaign after only a few weeks of play. These issues can't be patch, and if we return to the setting, we'll convert it to HERO System or perhaps Age of Heroes.
Speaking of the setting, like much of 40K- it's a mess with different authors having completely different takes on subject. Some view the Guard as complete tactical fools, others as professional warriors.This is perhaps expected given how large the Empire is, there is room for human wave style combat and effective modern tactics. It all depends upon which leaders and regiments one is looking at.
As a side note, our campaign was a deconstruction of the setting in important ways although on it surface it appears as much as written.