Yea i have to agree, I enjoyed the first 2 or 3 episodes but as it went on i quickly got bored.
I think there were far too many action scenes, not enough character and plot development. Dont get me wrong the action scenes were very well done, but it felt like it was a filler. I really wanted to get to know the other characters more, the technology and all the intricacies they seemed to leave out.
It was a shame as Rugal couldve been really good. It had potential, they had a great cast and like you said the music and visual aspects were good. The script really ruined it, I love the majority of OCN's dramas so it was a bit disappointing! To be honest i ended up jumping through the last 6 episodes to see Gwang Chul (i loved the actor, but the show made his character into such a lame person :(
ohh and can i do a special mention for Gi Bum's hair in the last few episodes, i couldnt stop laughing he looked so angsty (not in a good way)