I agree that the Noah and they're plot line is the more interesting side of the story, but I think the Noah work best when they're working off the various well established exorcist characters since it lets the Noah go into pure fuckery mode which is glorious. Link is a great character for sure he's really grown on me and he's interesting because it's honestly hard to tell where his loyalties lie and Kanda for me was residentsleeper.jpg why is he popular until the last 40 or so chapters where his popularity was justified by an amazing back story and his recent actions.
I also agree with the whole evil side of the order being needed as it helps to show how both sides of this conflict have good and bad elements to them which further works due to how split Allen is as a character both in terms of his desire to save Akuma, humans, and Noah but also his dueling personalities between Allen and the 14th. I'm just annoyed that Lenalee who's clearly in love with Allen (and Allen vice versa) has only helped cover for Kanda as part of trying to find Allen and bring him home, same with the others I mentioned because they'd clearly take Allen's side over the Order's.
It's a similar frustration I had with Bleach where the series established a bunch of characters I like, has kept them relevant power level wise... but just isn't using them or isn't showing them do anything and it's frustrating. The difference being of course D-Gray man's story is far better and more interesting and instead of focusing on characters we give zero fucks about it's giving more attention to the best characters so I can accept it.