Reading through the thread on Cata Healing below I was struck by several things that were said about changes in healing styles over the life of the game. The emphasis on the changes mentioned seemed to me to be concentrated on the "what" almost exclusively and very little if any on the "why". Lets look at the why for a moment.
Here are the only two reasons that I can come up with that could explain things in a more or less normal way.
1) With the introduction of a new x-pac the content of game in will no longer respond adequately to the healing techniques followed previously. (assume talents are unchanged and spells are proportionally more powerful for the sake of discussion). If that has ever been the case nobody has bothered to mention it here.
2) The changes represent fine-tuning. But that's not how it is feels to me.
That leaves something not normal. Something on the order of change for change's sake and that's what I think we got to a large extent. My theory is that they are going to keep on changing things every x-pac in order to keep a degree of freshness in the game. Obviously some classes will vary less than others from x-pac to x-pac but on the whole that's what I think.