Tau out of place? Like so many of their allies the people who say the Tau are out of place only see the face the Tau present. All the lives of the people in the Tau Empire are equal, the lives of the actual Tau, however, are just a little bit more equal than the others. Tyranids coming? Get the Kroot to set up some traps in the jungle and wish them luck while the defences are shored up. If they need support send in the Humans. The Tau don't believe in meaningless sacrifice, but do the Imperials not believe that any life given in the name of their Emperor is a life not given in vain? The Dark Eldar want 70 of each Caste and 7 Etherials for a 'cultural exchange'? Well, we can do without 280 of the other castes, but SEVEN Etherials?! The very nerve!
Why is Farsight holed up in the Damocles Gulf, and just how is he getting his hands on the newest kit like Sniper Drones and Special Issue wargear if he's not being supplied by the mainstream Tau? One possibility: As the propoganda suggests, Farsight wants the Fire Caste in charge; 'It's good to be King'. He's getting supplied by defectors and rogue traders. But this is the Tau, and as I've already pointed out you can't look at just the face. Maybe it's not Farsight who thinks it'd be good to be king of the Tau, but the Tau who think it would be good to be kings of the Galaxy. That's the other possibility, those are Tomb Worlds, or something similarly threatening. He's allowing himself to be villified so that some young Etherial doesn't try to colonize those worlds and disturb something that could kill the Tau Empire, and the Etherials (the would-be kings) are too ashamed to admit that Damocles is the sword that could potentially slay them.
I'd like to see Calgar make a sacrifice like that, the closest is Ventris' exile and triumphant return, in a setting where a heroic sacrifice is the way things usually go. The 4th should to be being led by the sargent that tattled on him for breaking faith with the codex, and his mental rigidity should see the 4th wiped out completely, with him having a horrible revelation at the last moment 'Ventris was right'. That's 40k; the good heroes are the dead ones, and the ones in charge are their own worst enemies!
The currently written Ultramarines are more out of place than the Tau. I read the newest Space Marine (and by Space Marine I mean Ultramarines) codex, and glorious victory after glorious victory is just not what 40k's about, ESPICALLY for the Imperials! That book does not convey the 'things can always get worse, and they will, soon' feeling that The Imperium is supposed to have. There is nothing rotten in the heart of Macragge, no desperation, no impending doom, no aincent shames or betrayals, and that's doing it wrong.
At the very least the Uriel Ventris vs Tau novel had the Tau acting like the bastards they really are.