Well, I feel like if all the stories involve champions trying to kill eachother, it becomes boring itself. A little one-dimensional. That said, I feel like maybe this piece touched too little on combat. It didn't really tell us much about the things Riven and Yasuo did during the height of the warring between Noxus and Ionia, which could've created an interesting contrast. It also would've given us a glimpse into Riven before her change. They tell us she was this badass Noxian warrior who took no prisoners, but that's about all they ever say.
As I've said elsewhere, "badass" is not a motivation. It's a trait. This might've been a nice time to give us examples of what Riven actually did, how she felt about it. Let us know if she was having doubts about Noxus from early on, or if she reveled in their warmongering atrocities until they came home to her and hers. Show us Yasuo's experiences. Was he as ruthless on the battlefield? That's not a very Ionian trait, if so, but it gives them a subconscious common ground. If not, what was it that made him kill his enemies so efficiently? Was it pride? Honor? Patriotism? A personal grudge?
They had the chance to answer a lot of questions about these characters through their experiences during the war, and it would've given us a little more action to boot.