The only healer I have played to 90 so far is WHM and for the record I am perfectly ok with "1-button spammed DPS rotation"
But I definitely agree with the OP's comments about consolidating redundant healing actions and having them simply evolve into higher forms. But then I feel that way about almost all jobs, would rather have actions evolve rather than keep adding more and more buttons. Two combat Hotbars should be plenty, not three.