Back during 1.12, boss hit points were hidden. Despite my best efforts...I have been unable to find anywhere that discusses the hit points of Ragnaros from when it was raiding content. This includes a couple of different strategy guides. The only thing I found was this following link:
http://wowraiding.com/40man/mc/bosses/mc_ragnaros.php
Note the estimated hit points found on that page. If there was a nerf to vanilla content, this post is the first I have ever heard of it. Admittedly the most I was raiding in vanilla was ZG pugs, as I didn't hit 60 until about 2 months before BC came out, but I have found nothing to support your claim that there was a nerf in vanilla, and the only thing I HAVE found supports the opposite.
As we explained, the nerf in BC was done specifically because of the change to game mechanics. The bosses in SWP were designed under the assumption that the raid would have drums and heroism up nearly 100% of the time. Both mechanics were changed so that they couldn't be chained in 3.0, so they nerfed the bosses. This same need was not present in Vanilla, nor was it present in Wrath, so I see no reason for them to nerf the content.
To answer your question, no they have not done a sweeping nerf as they did in BC. If they did, it would have been in 4.0. There is no reason to nerf it now that it is no longer relevant.