I know healer performance is nearly impossible to accurately measure, but from what I've seen Rdruids are 20-30% below the other classes and are almost non-existant in top guilds.
This is what I don't think I could ever figure out about the "WoW Community" - this desire to measure yourself against people who you don't need to be measured against.
When in a raid, what matters is that the boss dies before the enrage timer. If the healers chosen for that raid succeed in keeping those alive who assist with that goal, the healers did just fine. Whether those healers are Monks, Druids, Priest, Paladins or Shaman, it doesn't matter. If Uberpaladin is the best healer in the entire game and kicks out triple the healing of lowly little Druid me, that means nothing, because Uberpaladin is not in my raid.
Yes, there is an open market for raid spots. But for the vast majority of players, the market is not very open. If a healer is doing their job and not causing a bottleneck on progression, the raid leader has no reason to shop around for a different healer. (The market does open up when you're seeking to join the "elite" ranks for heroic world firsts, but that sort of min-max recruiting doesn't matter for almost all players).
In PuG situations, this problem has all but gone away. I remember in TBC being stuck because of the "This class is better than that class" problem -- I was a warrior tank, and when answering a call for "LF Tank for Heroic SH", I'd often be met with "Sorry, we'd rather have a Paladin". But for current PUG content, no group is going to say "Sorry Druid, but we hear that <insert class> is slightly better than your class."