I believe the position of the Devs is that it comes down to counter-play. Azureblight is a good example of this.

I am not arguing that there is/isn't counter-play to AB. I am only saying that lack of counter-play is the reason given for the nerf, "In addition to this, we're also removing the scaling damage effect when hitting an enemy player, as the sets unique functionality between multiple wearers can create some incredibly overwhelming experiences with no clear counter play. "

when it comes to NB running the mentioned sets, there really isn't any effective counter-play. NB can burst from cloak, and while you're left holding block and healing the NB can cloak away or, if you're in execute range (and not already dead) they can use their already overpowered kit to finish the job. There is virtually no counter play to this outside of running 40k health, two HOTS and spamming burst heals. This leaves you out of resources and the NB ready to rinse repeat or disengage and move to another target.

This is incredibly toxic and the real culprit isn't the sets, it's the combination of cloak, ridiculously overloaded class damage kit AND the sets.

Lastly on the off-hand chance you're able to survive the burst and return fire, you're hampered by the fact that you've had to build into survival so much that it's more difficult to x any NB worth their salt, especially considering they can crutch on the ridiculously overloaded heal that isn't impacted by battle spirit.

It creates an incredibly non-competitive environment, makes newbies less likely to stick around (unless they're running NB at a competent level), and significantly hurts the long term survival prospects for all types of PVP in this game.