From my guild, even though i kept telling them to take advantage of it, only like 1/5th of the people actually did it. Most didn't feel like it, mostly because all the weeks that they've done a +15 they mostly never got anything useful [myself included] I did mine and i carried 2 guildies through it. And then there were maybe, 5-6 others that did a 10 or higher. Somehow, i doubt many of people did it. I don't really care either, it made my life easier on my rogue alt and my main so im not going to complain about other people doing something that i myself took advantage of.
I didn't have to do a +15 this week, so i didn't, and i'm perfectly glad about it. I also don't care that others got to do it too. Sure it's slightly higher than mythic gear but the mythic raiders have access to it too so who cares.