For last two months or so from my experience in pc/na both PvE and PvP, the number of NBs have substantially dropped.
In cyrodiil, few patches ago, there used to be a swarm of NBs everywhere. Right now, magblades are virtually non-existant except the last few Caluurion gankers. Stamblades for the most part are just as rare. I remember being quite a few variants of stamblades in Cyro, from rollerblades, bleedblades, brawlerblades, onslaught gankers, melee gankblades, SnB sNB, speedblades, snipers. Of all these types. The only type that has remained is snipers and the occasional DK wannabe dizzying swing spammers. Even then, they are one of the least seen specs right now and the remaining ones are hardly any threat.
In Bgs, it is even worse as even during the NB's best patches, they were easily the worst class to have in your team. Right now, having Nbs in a team substantially increases the chance of the losing. Only spec that is remotely useful are the healer magblades.
Havent done much Pve lately but from what I hear from guildies, Nbs have become the tank class and no longer a competitive DD class. Going forward, that seems to be the case even more, as magdks, stamdks, stamplar and magsorcs all got unique utility buffs that can only be given by DDs and thereby 4 slots of 8 dps slots in trials is already booked, leaving the remaining for stamcros, magplars and stamsorcs. Nbs lack both utility and raw dps to be a DD contender.
I am getting a feeling that NBs are largely becoming irrelevant as a class with pretty much the only thing that is keeping them on the scene being Cloak.