I don't have 6.0 yet, but a coworker already got it and he doesn't have any trouble with Netflix or hulu.
Send an email to the Netflix devs to see if they have a solution.
My Nexus Player updated automatically to 6.0 and now Netflix won't even load. I've uninstalled, reinstalled, cleared cache and it still just grinds on the Netflix logo.
Maybe I should have called this thread 6.0 issues instead of focusing on just Netflix. I've just noticed a chrome cast issue where it doesn't display correctly with YouTube.
Netflix has all kinds of stuttering issues on my Nexus 7 (2013), video stalls out but audio keeps playing. Bunch of comments on Google Play from Nexus 7 (2013) owners as well saying the same thing.
For me it only occurs during HD video playback and if the wi-fi drops out and netflix is only playing from cache/buffer the video plays fine. I have a suspicion that this has something to do with Marshmallow rather then netflix.
Resetting to factory defaults to care of the casting issues, but the rendering of subtitles in Netflix is still there. They just pushed an update, but the issues are not resolved.