Nothing less, but unfortunately nothing more either. Which is sad, because I think it wouldn't take much to make this game feel good, like having proper music during the action sequences and more allied NPCs to give you a better impression that you actually are in a battle. Both are there, but the soundtrack consists of ambient music and AI teammates are few and far inbetween and most of the time, they only join you for a short time or get killed right away.
Which somewhat ties in to the "Fluff" aspect of the game. This is a mixed bag and while I understand that they can't stay 100% true to the lore, due to balance reasons, some of the stuff in the game just feels wrong. For example, a normal Imperial Guardsman can take up to 15 hits from a Pulse Rifle and a Seargent takes a full magazine before going down. And Pulse Rifles are supposed to be among the most deadly weapons in the galaxy.
An other issue is that the Pulse Carbine, the second Tau weapon you get, is horribly inaccurate and acts more like an SMG than the middle to long range weapon it is in the lore. Both weapons can be "fixed" when turning on auto aim, which makes the Guardsmen die faster, too, but you shouldn't resort to auto aim to make the game feel closer to the fluff.
I also think that the Tau military is pretty underrepresented in the game, because the only units you actually see in combat are Fire Warriors, but none of the others. No Stealth Suits or Devilfish transports, although both are mentioned in the tutorial, no Crisis or Broadside Battlesuits, no Drones, no Kroot, no Vespids, nothing.
So, what does Fire Warrior actually do right? Well, there is a good amount of weapons and aside from the Tau ones, feel actually reasonable. Lasguns and Autocannons are worse than Tau guns, Plasma guns burn the enemies and Bolters make the enemy go up in flames or make make them explode into little gibs. Equally, there is a good amount of enemy varitey and later levels touched by the Warp look nice.