Oh boy, here we go.
If I can sum up this anime in one word, it would be "disappointment."
From the predictable plot, to the animation's fluctuating quality, this show goes down the drain pretty hard.
The first episode of Juuni Taisen actually impressed me heavily, to the point of thinking it could be anime of the season. The fight choreography was spot-on, the animation had its own distinct look, characters, and it even had one of the best anime scenes i've probably ever witnessed. (At the end of the first episode, you'll know it when you see it.)
But after that everything is a train wreck. To say this anime is predictable is an understatement. You will know when a character will die, always. And there is no suspense because of this. To put this in perspective, it follows the 12 Chinese Zodiacs in order, it shows the entire characters backstory right before they die, and even in the very opening of the show it shows you in reverse order who will die. And that's probably the biggest flaw of the show.
Ignoring other plot points that never really got addressed at the end of the show, my other biggest complaint was the animation. The animation fluctuates CONSTANTLY. In the first episode, it's wonderfully and smoothly animated. Later on, characters lack details like faces , their hands and limbs look like doodles, and at one point for some reason Ox was missing a horn and in the next scene it was back in place. Then, it gets even more inconsistent with the introduction of heavy 3D CGI. Even while characters were standing in place, only moving their mouths, their entire body has been replaced with CG models. I have no reason why this decision was made, but it was a poor one.
At the end of it all, to all of those who died in the show, they all died terribly unsatisfying. Right when you think there will be an epic battle, somebody just gets stabbed and they die. This applies to every single character. They pop in, say their introductions to eachother, then they just die and plop to the ground. It's not a long drawn out battle or even a seat clincher. For a show in the genre of and based around action, there's a significant lack of attention to it.
I can really only recommend this show if you're bored and just need something to fill that gap. But if you are looking for something with substance or even mindless action, you're gonna have to look elsewhere.