They have noted in a few patch notes and regulation updates that they have worked on the summoning of Darkmoon Blades but people have still been complaining.
Honestly, the underlying issue could be that not that many people are wearing the Way of the Blue and are trying to get summoned themselves. I'd also wager that the playerbase has fallen off dramatically since launch save for those still interested in end-game stuff or challenge runs.
I think it's working as intended, I've had a blue/darkmoon summoned every time I get invaded, and that's with my level 120 characters.
Nobody using the Way of Blue is the issue, maybe if FROM started rewarding WoB members with chunks, more people would start wearing it.