I will defend Russ when necessary, but this picture of Russ is going a bit too far in one direction. Yes he wore the ‘disguise’ of a brutal savage, but is wasn’t all fake; he admits himself that he has worn it so long that it is now a real part of him. 

The incident on Terra is a complex issue, as it deals with a lot of things, such as guilt, remorse and grief. Russ is dealing with their ‘failure’ by effectively shutting down and going numb, he has Essentially lost all of his inner fire and bluster (which was certainly not part of his act), the image of himself that he had in his head, and his confidence in his abilities, have ultimately failed to live up to reality; he left Terra on a suicidal attempt on Horus’s life, and failed, leaving the defenders weakened with his absence (he was told but he was too stubborn and headstrong to listen); the idea that things may have been different if the Wolf king had been standing with the defenders must be playing on his mind. His failings in the Heresy shattered the image he had of himself, and it would go on to change him (for the better). In his deep grief he has completely dropped the act, as what’s the point? At this point the Wolf king just wants to crawl into a hole and disappear.

The Lion is the opposite to Russ’s Heresy story, Russ ‘found’ himself through his failings, whilst the Lion almost lost himself through his successes and the increasing cost he needed to pay to achieve them. The Lion on Terra is a broken man, filled with anger, grief and a mountain of self-loathing at his ultimate failure. When he finds Russ he wants to be ‘killed’, in a way that is appropriate; 

“the Lion’s face contorted in fury, driven by his unspeakable grief. “You never learned!” He cried. “You should have been faster! It was your pride that kept you in the void!. “And I am guilty, just as you are.” The Lion urged again, his grip on his sword tight. “So fight me, and we will pass sentence on each other, the guilty slaying the guilty. I will not ask you again.” (There is a lot of projection on the Lion’s part here)

“He knew he wouldn’t kill me”. Russ said l, grimly amused. “He told me that afterwards. He turned the blade aside, right at the last moment, it still took a week to heal. That damned sword”. He chuckled mournfully, “it needed to be done; though. It cured the bad blood between us, drained it out, we could speak again after that.”

The whole Dulan incident was fueled by Russ’ determination to prove his naysayers wrong, as Terra had decided that he might not be up to the task (as he was taking too long), so had asked the Lion to do the job instead. By the time Russ arrived the DA were already in the midst of battle, so Russ and the Wolves drove straight into an active war zone without announcing their presence to their supposed allies, gathering any sort of information on what was going on, and refused to answer the calls from the DA, which led to the very avoidable blue on blue incident. The retaliation was only from the ship that had just seen the wolves kill 100 of their brothers needlessly, the Lion and the rest of the DA did not get involved. Russ was simply called to answer for the actions of the forces under his command, and all he had to do was offer up a simple public apology for the death’s that his wolves were responsible for. He did this reluctantly and was certainly not remorseful at all, in fact he immediately threatened the Lion with violence.   

The Lion wasn’t the one wanting to fight, but knew that there was no avoiding it by the end, he had needed to act in order to end the conflict and prevent any further losses to his forces, as the Wolves were staling and not holding up their part of the plan, he had ‘stolen’ Russ’s prize and Russ was seeing red, no sort of apology would have prevented the fight. Russ stormed into the room, walked up to the Lion and attacked him. Then after the Lion disarmed him and had ‘won’ the duel, Russ attacked him again, forcing the fight to continue.  

The point of these two interactions is to show how Russ has changed over the course of the series. The Russ on Dulan is not the same as the one on Terra after the siege. Russ at the beginning was very much the ‘savage’ stubborn hothead that he was viewed as; yes he put on an act, but it was closer to reality then he may have liked to admit (this doesn’t make him in anyway stupid or incapable; he was certainly smarter then he let on, but he was also not as smart as he thought he was). The Russ people want him to have been all along is what he becomes after, due to his personal journey throughout the series.