@ShinGetsu: Yeah I feel the same. I see this happen once in a while with Shonen. The author gets desperate to up the stakes and shows off the bad guys being super powerful and stuff. But they go way too far and it ends up breaking the series because then it feels forced when the heroes make a comback.
Same thing happened in the last arc of Bleach. The author introduced those super powerful quincy and it was like "OMG THESE GUYS ARE INSANELY POWERFUL! EVEN THE BADASS CAPTAINS ARE JUST BIENG TOYED WITH!". But here was the thing.... they are so onesidedly powerful that when it came time for them to lose the author had to do things like invest weaknesses that somehow didn't come up until that moment, or pulled ass pull after all pull with the heroes getting power ups in order to win. Then after a bit the bad guys would reveal their hidden trump cards and one sidedly dominate again until either the good guys got ANOTHER power up or the main bad boss kills off his own subordinates.
The result was an arc that by all right SHOULD have been epic but instead it just felt like a coin flip of which side would on sidely dominate and none of it felt real. Yes we know this is all fantasy but the writing needs to flow in a way that almost feels genuine and Bleach failed to do that at all in it's last arc. It was just the author going "look at this cool stuff I can write... okay now move along nothing to see here".
Although in a way I think Onmyouji is doing it even worse. It's not just making the Basara one sidedly powerful to be epic. IT's trying to be dark and tragic and is relying heavily on shock value over death to keep up the drama..... except it's abused that so much that I got numb to that a long time ago. It's fine to have the good guys lose, after all if they only win then it's boring. But having them only lose and in such a one sided and over the top fashion then it's just as bad if not worse.