I hate to admit it, however, but my heart doesn't always fall in line with my head, and the recent change to Glory of the Dragon Soul Raider is one of those. You'll notice that the screenshot of the achievement above has removed the requirements of having to have killed heroic Spine and Madness of Deathwing, two fights I had to push my face through in order to get the mount.
This is where I turn into a hypocrite, I guess, because I don't like this at all. Not even a little bit. Especially with recent news that Blizzard is going to make the mounts off of heroic Ragnaros and Deathwing harder to attain in Mists of Pandaria. So you're making the drop mounts harder to get but the achievement mounts easier? And frankly, taking heroic Spine off of this achievement doesn't just make it kind of easier, either; it makes it massively easier.
At this point, my heart and my head are in full-out war over this. Like I said, intellectually I support the progressive reduction in difficulty as a good compromise that lets people see more content while it keeps progression moving forward.