I honestly don't see how its very different from the Ground of Strength stun proc that was nerfed in a heartbeat ages ago. NCC= passive 4 second silence chance that procs off MM/ranger attacks as well as Sabo and ranged nightblade attacks, even aoe attacks liike fan out.
NCC doesn't only affect mages and clerics, but prevents you from using many warrior (especially riftblade) and rogue abilities as well. Marksman already has an interrupt / 5 second silence on a very generous 10 sec cd (with rapid extrication), NB has a 5 second silence opener, and ranger has an AOE interrupt/5 sec silence finisher on a 30 sec cd. BD also has a ranged interrupt/5s silence on a 10 sec cd.
As a mage if I want a silence in a dps soul I have to go 32 points in warlock for a 5 second silence on a 40 second cooldown (or go elementalist and use the greater water pet LOL NOPE)
In the past I would have argued that rogues need tools like NCC, but they have gotten buff after buff since release and their dps and utility has gotten to a level where I think this consumable needs to be changed completely or at least not proc off aoe attacks.
Flame on, PvP forums.