Please read what I wrote again.
I have yet to hear of any such fan fiction. If you disagree, though, feel free to go read it.
Bioware has no reason to make apologies for Revan and the Exile being beatable. As far as I'm concerned, the Revan novel did nothing but take these two characters that the fanbase exalts as the greatest and wisest Force-users ever and make them actually just a little bit human.
More to the point, canon is an editorial necessity since these stories are part of the larger Star Wars EU, and there has to be an official version of these galactic events if any subsequent stories are to make reference to it (and not allowing future authors to reference the KotOR games for the sake of some fans' egos would be absurd). If you don't like the official version they come up with, well, you don't have to like it. And you only have to accept it if you're in a debate with someone which requires the whole of the EU to be taken into account. Just do what I do with all the EU I don't like (Jedi Academy trilogy, Karen Traviss, New Jedi Order series, Legacy of the Force, etc), and don't like it.
Ah, the classical position toward Revan. You're wrong.
It's late, I've debated on this many times before, this forum is a bad habit anyway, and I sort of hate myself, so I'm only going to explain why you're wrong once, in a numbered list with subtitles for your convenience. Consider this my reply to you to end all future replies to you, as well.
1. You are accepting Kreia's every word about Revan as fact despite the fact that she is unreliable - As we see in abundance throughout TSL, Kreia tends to have very, very strong opinions about her student, particularly whenever those opinions are about whether he was justified in his actions. Worth noting is that Revan is known for defying the Jedi Council many times in his actions, and that Kreia has an intense vendetta against the Council for denouncing Revan and her. Kreia despises the Council and their decrees, considering them to be set in their ways and unwilling to stand for supposedly being proven wrong, and feels betrayed for how they blamed and exiled her for Revan's turn to the dark side. Kreia lost her life as a Jedi Master because the authorities over her wouldn't accept her greatest student. She equipped Revan for everything he did, and then lost everything because of it. She therefore has a need to justify Revan, and therefore herself, in order to believe that her life hasn't been a waste. Is it not telling that she absolutely never in TSL says anything whatsoever about Revan that is negative or critical, never says anything about him except what a great guy he was? Also noteworthy is that she claims to know quite a lot about Revan's motivations, but has no way of actually knowing so much about those motivations after Revan left for the Mandalorian Wars, since we have no evidence that the two were in contact during or after that period. In short, Kreia has several major self-serving reasons to portray Revan in an unrealistically positive light and to pass off his actions as being for the noblest reasons imaginable. There is very little reason to consider her an authority where Revan is concerned.
2. Revan did not become the Dark Lord of the Sith out of any necessity, whether we accept TSL or TOR's theoretically revised version of it - The soundness of Revan's joining of the Mandalorian Wars is debatable. On one hand, the Jedi Council was initially doing little to deal with the invaders. On the other hand, Revan was being reckless in leading a large number of Jedi in direct defiance of them under his own command, inviting the possibility of some sort of disaster befalling them on account of his unchecked leadership (which eventually did happen; worth noting is also that the Council did give Revan their support against the Mandalorians after the genocide at Cathar was revealed to them per the comic, Masks). More important, though, is Revan's actions after he had been fighting in the war for a while. We are given plenty of information even as far back as KotOR I (the computer guarding the Kashyyyk Star Map, especially) about how he conducted the war, being willing to allow preventable deaths in order to strengthen his own public image. In TSL, Kreia (on Dantooine after slaying the three Jedi Masters) goes into detail about how Revan deliberately used the war to corrupt his Jedi to the dark side and to loyalty to him ("The Mandalorian Wars were a series of massacres that masked another war, a war of conversion"). HK-47 (and several others) also note that Revan deliberately worked to have certain individuals under his command killed in the war - specifically, those who were not loyal to him personally and therefore wouldn't follow him when he betrayed the Republic. This directive culminated in Malachor V, where Revan deliberately used a superweapon to massacre both the Mandalorian fleet and his own fleet, composed of officers he determined wouldn't follow him, with the side-effect of shattering the nearby planet and creating a wound in the Force. Now then, with all that out of the way, the question remains of whether for Revan, knowing about the Sith Empire in the unknown regions eventually wanting to come get revenge on the Republic, becoming a Sith Lord was justified. The answer is no because after having beaten the Mandalorians, Revan could have told the Jedi and Republic about the true Sith (his findings on Malachor would have been more than enough to convince the Jedi Council). Instead he took his fleets and armies, made all of them into Sith, and declared war on the Republic - this act was in no way prompted by any dire situational circumstances and can only be explained by a desire on his part to rule the galaxy. Whether he eventually was made into a herald of Vitiate is incidental to this; Revan already set his plans to become a Sith ruler in motion before the two ever met.
3. Revan's actions caused a lot of horrible repercussions - Revan created a Sith Order which spawned the likes Malak, Jorak Uln, Uthar Wynn, and countless other despots and narcissists (none of which, it is ever hinted, he ever disapproved of or punished the brutality of despite Revan supposedly caring so much about reducing collateral damage), as well as Sith assassins who tortured captive Jedi into converting. He is also indirectly responsible for Darth Nihilus and Malachor's wound in the Force (which he may or may not have been able to forsee). Needless to say, absolutely none of this was necessary in order to protect the galaxy from the true Sith.
4. There is no evidence to suggest that Revan's actions nearly prevented a greater evil because he was no better than the "true" Sith - What did Vitiate plan and eventually carry out 300 years later? Invade and conquer the galaxy with his Sith Empire. What did Revan do? Invade and try to conquer the galaxy with his Sith Empire. And there is nothing fundamentally different about the two Empires, as far as how well the galaxy would've fared under either of them. Vitiate's empire was extremely Human and Pureblood Sith-centric, but as we see in KotOR I, the Sith of Revan and Malak's empire were just as racist, at least in the rank-and-file membership (though it is notable that very few Sith in the game are non-human). In the end, both Sith rules destroyed planets and killed Republic military members, Jedi, and civilians. There is nothing suggesting the galaxy would have been better off under Revan. If anything, his noble goal of saving it from the "true" Sith is merely how Revan justified his goals of conquest himself (and again, this is generously assuming that Kreia knew anything about what she was talking about when speaking for his motivations); he wanted to save the galaxy for himself.
In brief - The supposed gray morality of Revan in TSL is a lie that Kreia invents to justify herself and him (and for the record, I like the story of TSL not because it's a tract about how ****ing awesome Revan supposedly is, but because Kreia's character is written in such a powerful way). Whether you believe TSL, TOR, or both, Revan became a Sith Lord, killed a ton of innocent people during and even before that period, and tried to conquer the galaxy. Best-case scenario, Revan was a egomaniacal, sanctimonious, treacherous, delusional mass-murderer who successfully fooled himself (and his old master) into believing that his selfish desires for personal power were noble intentions to "save" the galaxy from others, and the only reason he was better than Vitiate himself is that unlike Vitiate, he didn't want to literally consume all life in the universe.
So, yeah. Revan's not a good character because he was so awesome that he was able to transcend morality and the fundamental rules of the Force in Star Wars. He was a good character because he's a tragic figure who began as a hero, fell to evil despite having good intentions (and likely justified it to himself along the way), but then was given a chance for redemption. And in the canon he went down fighting for what he believed in. Except in TOR the game; ironically, his last appearance to date in that game has him pulling the exact same routine as in his Mandalorian War days. Good enough for me aside from that last part. You're free to think what you want, but unless I've completely misinterpreted your position (which case I guess I'll just have to live with myself), you're wrong.