@Vergift In Kurenai's defense, fighting wouldn't have done her much good during this arc since killing Deido would allow the invaders to enter Souboutei. She's been plenty badass throughout the rest of it, it's just been a while since she could show off.
I also don't get people saying Oujin is boring. If you compare him to Deido of COURSE he seems boring, Deido is a one-of-a-kind villain. But in a way, he's also the opposite of Deido. All Deido wants to do is create art, nothing else matters to him. Even when he used his power over Souboutei to slaughter a bunch of people, he didn't really show any emotion except annoyance at having his painting interrupted. Oujin meanwhile wants nothing but destruction, and visibly revels in causing people pain and suffering. Deido doesn't care if the world ends, while Oujin specifically desires it.
They're basically written as foils to each other. The personality clash was pretty much guaranteed, but it still manages to break from the usual formula a bit because Oujin is actually pretty clever. Usually in this scenario the apathetic one wins hands-down because they're not controlled by their rage and all that, but in this case Deido's powers are completely connected to Shino, and Oujin already has powers beyond what Shino can offer. It seems pretty likely he could have died in this chapter if Kurenai hadn't jumped in.
Just all around an awesome chapter.