Truthfully, I'm struggling a bit to follow your train of thought here. You say that dungeons in HW were easy, but healers still felt critical. You say that mechanic damage output in HW was similar to EW, but HW required far more healing. That HW dungeons weren't complex, but a midcore group could not pull off a healerless dungeon run.
These statements are honestly just reaffirming my point that the main culprit is the battle content. As all of the jobs have gotten stronger, a lot of the content has not kept pace. Healers have so many tools, but nothing to use them on. Instead of trying to go back to "the good old days", I'd prefer to move forward with the current philosophy surrounding job design and see how else players can be engaged.
Interviews from the recent Media Tour have said that they are planning to focus more on job identity starting next expansion (and possibly during the patches leading up to it), so maybe you'll get your wish with added complexity to the Healer jobs. I just hope to god they don't start heading back to where the game was in HW/ARR. I personally didn't raid during those times, but from everything I've heard and read, the best words I can use to describe it are "obtuse" and "inconsistent". Some jobs didn't even function properly and were not even allowed in a group.
As an aside, I did raid during StB (starting playing in HW casually) on a different character. But that's not really important and I'd rather not get into a measuring contest.