Say what you will about the game, but the novel gave a CMOA to the Voice with an Internet Connectionof all people. The narration keeps cutting away from Kais and Ardias fighting the Greater Daemon to Lusha and his squad suiting up in their Crisis Battlesuits. Aside from quite neat detail of how one operates a Crisis Suit, this seems quite irrelevant as you think 'so Lusha's going to go shred Chaos Marines while Kais FIGHTS THE FUCKING Big Bad!' Wrong. After Kais uses the dud bolter shell to destroy the last shrine, Lusha and the Crisis Team come screaming in and proceed to unleash Every. Single. Weapon. on their Battlesuits, blowing the Daemon back to where it came from. Awesome.
Aside from the CMOF which resulted, Kais blowing up the Titan is pretty awesome.
And Ko'vash. Hell, Ko'vash. The new Grey Knights Codex broke the base when it gave us incorruptible Grey Knights, but the novel of Fire Warrior gave us the incorruptible Ethereal, and it made perfect sense. The Daemon literally cannont grasp any sort of purchase in the guy's mind. Compared to how easily the Admiralfalls, Ko'vash deserves a medal for effectively giving a Greater Daemon the finger, without saying a word. Bonus points for the Caste name of the Ethereals adding a little Fridge Brilliance, their emotions are so in check that they basically are mentally untouchable.
Khorne gets one for being subtle, for once, guiding Kais throughout the story.
Lusha's response to the Crapsack World that is Warhammer 40000? He admits to Kais that the Greater Good doesn't exist (keep in mind, the Greater Good is as big a motivation to the Tau as the God Emperor is to humans, a comparison directly made by Ko'vash), but that striving for the ideals it represents is enough. Even faced by a totally dark and cruel universe, Lusha chooses to be the Anti Nihilist.
For the novel, Word Of God has stated that Shas'O Kais, the Tau commander in Dark Crusade is the same character as this Kais. That means that in the end, Kais overcame the trauma of taking on the forces of Chaos and Took a Level in Badass to become a Shas'O.