And yet Blizzard caves again. Well done on staying with a decision regardless of how much people whine. Well done.
It is not really a matter of caving to whining, but more a matter of protecting the gameplay experience of a lot of players - many of whom who aren't even raiding.
The design intent behind this boss was for him to serve as a world boss for very organised guilds rather than pickup groups. However, since it is possible to overwhelm Oondasta with sheer numbers, players were massing around Oondasta every time he spawned in such great numbers that it brought our servers to their knees. An Oondasta fight would often result in a slideshow-like gameplay experience for those players near Oondasta (unless they are the lucky owners of powerful gaming computers), and in those cases where an Oondasta raid caused the entire continent of Pandaria to crash, an even greater number of players had their gameplay interrupted.
As you can maybe gather from this, we simply do not think that this is an acceptable experience for our players, and so we reduced Oondasta's health, so that smaller groups are more likely to down Oondasta before so many players arrives that it degrades the experience for everyone present. We chose to do this instead of buffing his abilities to such a degree that he would become un-killable. For an example, we could have changed Oondasta to make him un-zergable by for an example equipping him with a Spiritfire Beam that could hop to 99 targets instead of 20, and a Doomwalker-style debuff that prevented players who had died during the encounter from re-engaging. But such a change would not result in people to stop massing and continuously try to defeat him, instead it would have resulted in a world boss walking on mountains of corpses that no one could kill, and thus turning him into a frustrating experience for most if not all players in the long run.
The Oondasta encounter clearly did not deliver on our original expectations and intentions, and we would not have lowered his health if our server capacity were limitless. However, since this is not the case, we felt it best to choose the lesser evil and reduce his health and then instead apply the lessons we have learned from this experience to any future world bosses we may add... Bosses that would not be so zergable...