IMO they should have made the Tau not evil (make the mind control vibes just imperial propaganda that is the result of actually encountering people motivated to do good).
As it is, the Orks seem to be the least evil faction.
> As a bit of an analog for late 20th century / early 21st century western interventionist culture I've always assumed that the Greater Good is ultimately for the benefit of the T'au and if others get something out of that's just a bonus. The fact that they are even willing to work with other species is pretty unique and progressive among the factions of 40K, rather than rampant genodical, xenophobic armies. The thing about the Great Good is that it is, in the long term, as inflexible and authoritarian as the Imperial Creed or the all-consuming Tyranids. It still comes down to the Greater Good or Death (tm). I've tried not to make it too sinister being within the T'au sphere, though in the original Apocalypse book I introduced a variety of NATO-style innocuous three-letter-acronym formations, like Mobilised Hunter cadre, Dispersed Retaliation Cadre and Forward Commitment Contingent. None of them say 'battle' or 'war'... I cazn imagine the news back home is quite a sanitised version of the reality - like when we watched videos of 'smart' bombs and gun cameras blowing up stuff in Iraq but were totally unaware of what was really happening on the ground.
You're right about the Orks, of course. They're just out there living their best life! #GreenBoySummer
[1] https://www.reddit.com/r/40kLore/comments/b3pc01/qa_with_gav...
A lot of the stuff the Imperium does is not just evil but also stupidly counterproductive. Planets starving due to rounding errors in the filing system is hard to take as an endorsement. And I couldn't disagree more with the Tau, if anything I wish they had made them more sinister. Having a whole faction of non-tragic good guys in the setting really spoils the vibe.
But the Orks - agree so hard. There's a quote in a Codex somewhere from an Eldar philosopher waxing on the point that the Orks are thriving and living their true lives, while the Eldar are decaying as a result of their own corruption and therefore the Orks are morally superior, and it rings quite true.
Well, it is written off like that in lore too. "We do bad things because war machine needs to be fed, because our entire existence depends on it" is recurring theme.
Even the "good" Tau are pretty fucking bad when you start looking into their practices of casual eugenics...
Frankly only non-evil-at-core one would be Tyranids which are only hungry
Strange as it sounds, imo the least evil faction is the Tyranids. Though they're (or I guess technically it, because they don't have individual minds) intelligent, its an entirely different form of intelligence which makes them more like a force of nature, no more evil than a tornado is.