I am on a 5on5 team within the 2100 points range as a feral druid.
I do not think it is as bad as people make it out to be.
My team consists off: Warrior/Paladin/Hunter/RestoShaman/FeralDruid
I just will describe my duties as the 0.5 healer within the team and if I feel useful enough.
Surviving:
I actually never get focus fired. It is amazing. The Hunter/Shaman is always attacked first and I never died because I had bad survivability ever due to bearform. Bearform could use some magic mitigation though.
Travelform is not as useful because a feraldruid is usually in the middle of the heat.
->A Druid needs 2 healers to make bearform truly viable. Otherwise its just the "die slower form".
Damage:
Since I am most of the time free to use my form of choice I take catform on this one. (obviously

)
Our Damage is great while we do not do anything else. We can easily stay on a target and provide semi manafree, very high burstdamage.
While featuring 149% speed due to the gladiator set bonus it is simply trivial to shred harmstringed targets. Even if you decide not to blow the mana for breaking the snare, your energy is still regenerating and your damage will be even more bursty. Depleting 3 shreds for 42 Energy for 2700 damage per crit within 4 seconds is simply amazing burst.
While my damage in bearform is lacking I can still charge to a harmstringed target and stay on it because I am simply faster (while harmstringed myself) and my bearform does more damage to your squishy than your warrior does on my 14k armor. Sometimes I simply choose to stay in catform and tank one warrior.
(Having the warrior on myself frees up our hunter to do his shot rotation and that nearly doubles his damage)
-> No meelee class works without snared targets in a group situation.
Healing
I got about 6500 mana. Switching to my healer staff I feature roughly 730 addhealing.
You will not out heal anyone as a feralbuild though. I usualy switch to healermode if my paladin or shaman cry "sheeped", "counterspelled" or anything similar into their microphones. I am there to cover the healing for a few crucial seconds. This is also the point where I switch to defensive cycloning.
Tranquility is amazing for that job.
Problem: Druid heals are designed to work over time. So the classes healing style does not support my roll as the emergency healer perfectly. (no NS/Swiftmend)
Usually I can buy the few seconds needed for my healers to recover.
Crowd Control
A druid can shut down 2 healers at the same time for about 9 seconds with a combination of bear and cat. One target can always be cycloned.
Usualy I only cyclone healers while
a) I need to shift anyway because of a snare/root/...
b) I just blew my finisher and need energy anyway
c) I feel the target will die
-> all of our CCs need to be maintained.
If I would draw the conclusion at this point I might say, that I am very pleased with my druid.
I usually do not feel like a 2nd warrior would better complement to our group. I do not need to be maintained by a paladin. I do not need blessing of freedom to function.
Harmstring and Mortal Strike are applied already.
And I realy feal far superior to rogues, that can only function until all cooldowns are blown.
Here come the downsides: (warning: contains some QQ ^^)
Shifting kills all the rage and energy you have.
I use Staff of Natural fury and I still pay 590 mana to get into bearform to charge/survive and 590 mana to get back to catform to make damage again.
Additionaly you get a global cooldown after shifting into a form.
That said you can not do CC+Burstdamage like a mage. A mage can wait for a crucial moment, counterspell, AP/Pom/Pyro to do controlled burstdamage while both of his crowd controls are active.
This is also the reason why Resto+Cyclone is officially better. You do not need to switch between primary roles.
Switching to a hot healer with no hots running.
Switching to a rogue without energy.
Switching to a paladin, that can not heal himself.
As a feraldruid you can only fullfill one roll at a time and you are penalized so heavy for switching it is not even funny. All CC spells are simply too short to allow any synergy between forms.
In conclusion:
All druid roles work fine within the right condition, but switching between does not.