xcloak has worked for the last 2-3 updates including their other app Ping It as well as SkyGo etc as it sits on the framework between the actual app and fs, they're going to struggle to stop it, one of the major reasons that xposed is so popular on XDA etc
OK I might have have to give it a go.
Also see below I pasted from google boards if you still have an issue with video hiss
Hey everybody. The fix got its own thread over on xda: http://forum.xda-developers.com/google-nexus-5/general/mod-camcorder-audio-quality-fix-t2837930/
This is the real deal fix for this issue. We can all now enjoy fully functioning Nexus 5s now. Be sure to give chdloc a thanks for coming through for us.
Turns out it absolutely was a problem with recklessly aggressive noise canceling software after all.