Firstly, welcome to the forums.
Next is I wish my response to your entry wasn't along the lines of telling you that you are preaching to the choir. A lot, and I do mean a lot of people here on the forums will agree with you. Unfortunately when that is the case, then it also becomes very difficult for you to provide a fresh perspective on the matter, and to interact with those who do oppose your views. In case you are not aware, there are many healers who support current healer design. Crazy, right?
The other thing I will mention is the devs do not create this false expectation that the players carry into every expansion. This is created by the players themselves, and I would even go as far to say the devs make sure to let the players know that encounter design isn't changing. Yet, they will still carry the expectation regardless.
Anyone who thought Sage would be this breakout healer that would "change the game" is the epitome of that false expectation. Most knew that despite all the fancy animations and a few more DPS options, SGE was still a healer at the end of the day. It is those players who are enjoying this job right now. It is also those players who have actually noticed that while the core concept of the job is the same, the manner which a SGE supports the party actually has them drawing upon their resources differently. In that sense, it has changed how a healer prioritizes their skills, which can make it feel quite different and take some getting used to. Just ask the many tanks who ate the floor with a SGE healer this past week (many of whom anticipated it).
I assure you, SE isn't frightened about anything. That's the echo chamber influencing your thoughts. They are however, conscious of how fallible human beings are, and that the very nature of the healer role is reactionary as a result of that. Healer is not the best role - nor should even be in contention, when it comes to optimization. There is another role in this game that is purely designed entirely around that concept and you know which one it is.