TLDR version: If you want druids nerfed, invite them to your 5v5. Complaining about a class you did not deem good enough for your team impresses nobody. Especially not the people balancing this game.
I chose 5v5 because it suits my argument and because nerfing ANY class that is dead last in ANY bracket is nonsense. This applies equally to all classes (my alt is a mage, who are in the opposite boat as druids).
I don't care about other metrics. Why? Because they are self-serving theorycraft. I have seen paladins theorycraft how they are completely useless in highly rated 5v5. Clearly that is not the case.
If the other metrics hold any value, they will sooner or later show in representation. Simple mental exercise. Imagine moonfire did 1000000 damage. Tomorrow, all top teams would have druids, and probably nothing but druids. You are trying to get ahead of the trend by balancing around metrics that show themselves before representation, since representation always lags behind. That is a noble goal, and also completely unrealistic because YOU CANNOT PREDICT THE FUTURE.
I remember, when gib teams rose to power people predicted that by the end of season 2 druids would be highly represented in top 5v5, because people looked at the success of a few gib teams and deduced that the ladder at the end of S2 would be nothing but druid based gib teams. They were wrong. What gives you such supreme confidence in your predictions? And do you think Blizzard will really risk it? I will make a bold prediction here, they won't. Why? Because the last thing you want to do when you are running the most financially successful game in history is mess it up by taking wild bets. They are conservative. They take things slow. Now you want them to change to fix things BEFORE they even become a problem. Ask yourself, is that anywhere near realistic?
This has nothing to do with the strength of druids in 2v2. I have said many times, a nerf to CC is a much bigger hit to 5v5 than 2v2. As such it is a non-starter from the get-go, because ANYTHING THAT NERFS THE LEAST REPRESENTED CLASS IN THAT BRACKET IS UTTER STUPIDITY FROM A BALANCE PERSPECTIVE. If you have a change that equally nerfs 2v2 and buffs 5v5, lets hear it. I have seen none so far. It is a hard problem to solve.
P.S.: I will not theorycraft about what could be workable with druids and what could not. It is a waste of time. Top players are like mice. They are good at sniffing out the cheese. If druids were the cheese, they would notice. Look at Pandemic. Hunters and rogues turned out to be poor choices for 5v5, and voila, they kicked them and put in an elemental shaman. I have no doubt that they would do the same with a druid if they deemed it advantageous. So I don't have to theorycraft. I can just look at people who are better at this game than you and me and see what they are doing. Actions speak louder than words.
P.P.S.: I know what works with a druid. I play one, in a lineup that works relatively well. I also know what does not work, but due to what I said above, discussing it is moot.
I said that druids are overpowered. You chose the measurement of druid representation in nebulously defined "top 5v5 teams" yourself. You chose it because it is their weakest bracket and by picking it and defining top teams however you like, you are best able to convince yourself that your class is in fact underdogs in arenas and you are succeeding despite long odds.
Despite this straw man you have set up, I will even take up that call. I argue that class power is not the only determinant of top - however you are defining top - 5v5 teams. I gave a list of 7 other factors which also influence team composition, and the list is not complete by any means.
However you still insist on using only one, flawed, metric - class composition of "top 5v5 teams" - to measure class power. I suggested a better and more complete and logical metric involving trends in all brackets, but you just went right back to "top 5v5 teams right now." Why? Because it is the data set that you found that most supports your need to feel an underdog. If you played a mage, undoubtedly you would refuse to count any division other than 2v2, and you would focus on the trends because mages are weak and getting weaker in that bracket. You are cherry-picking data to suit your bias.
So there's a tangent of me getting offended by unscientific thinking. I like science and will stick up for it! But to move back to the main issue: even in your chosen disadvantaged ground of top team 5v5, I beleive the druid class is a much stronger healer than it is currently getting credit for.
As more druid players and their teammates get used to their relatively recently added strengths, and more hardcore PvPers reroll to them (I beleive Tyveris is leveling one atm), their success can only increase. This is due to the class mechanics of having the best instant heals, the best battlefield mobility, the best crowd control, and the best (debatable with paladins) resistance to control. These strengths, while more readily apparent in smaller brackets, are still very relevant in 5v5 at high levels of strategy.
A plea for anyone to debate these strategic points on the basis of strategy, without mentioning the compositions of current top 5v5 teams. I have just spent multiple posts explaining why those compositions are a starting point for debate, not an ending point.