I'm a newbie on the actual forums, but I have been watching Paul's videos for some time and I helped fund his kickstarter campaign. (I'm not a special snowflake, just giving facts.)
I was very surprised to hear you are only getting 10% of subscribers to become viewers on YouTube. I don't know how the back end of YouTube works in depth but that number seems low to me.
One thing I know many video makers do is ask their viewers to share on FB and Twitter. I realize those lines can feel repetitive, but if you can get the 10% who are watching to be more active in helping you promote your vids, they might attract more high-quality subscribers who will also, you know, WATCH.
If you took one of the suggestions above and learned how to get YouTube to help you build views as well, then you would have the possibility of creating more high-quality viewers too.
I for one will take my own suggestion and begin helping you promote your vids on social media.