I maxed out the Sunsinger Subclass on my Warlock and have not been awarded this achievement. I attempted a full power reset of my system to try and get it to register, and it did not work. Please rectify, I would like to get my third Hunter started up as soon as possible. Thank you.
Hi Chase, As suggested before, sometimes achievements can take a bit to register. We have a help article on this issue here: http://www.bungie.net/en/Help/Article/12242
Sometimes the achievements take longer than expected to show up. No need to wait around, just move on to your awesome hunter!
I assume you maxed out both subclasses. You only mentioned sunsinger and I'm pretty sure you need to max out sunsinger [i]and[/i] voidwalker to get mastery.