I am running a team of five druids at Level 90 atm, so I maybe I can give some impressions. I boosted them to 80 and quested them up to Level 87 afterwards. At that point I startet running instances as an addition to the questing.

The leveling part up to 87 I did with five boomkins. It is very rarely necessary to use anything except moonfire / sunfire. Quest mobs will still have a few seconds to run to you and will then form a nice ring of loot around you. I really like playing with dots because you don't have to run around so much, all while having full mobility while doing it.

Anyway, from 87 I switched to a classic tank, DD and heal comp, in my case bear, 3 owls and a tree. The combination has its upsides and its downsides. The biggest downside is probably the eclipse-Management, but with Jamba that is very doable. My DPS ist not that awesome though, but I hope that will change a bit with gear. The ability to put 4 hots on a target (i.e. tank) is fantastic. Especially while leveling up the Boomkins can really each heal a ton compared to the health pools of the toons.

There is one talent that increases damage by 30% or so and allows part of the damage to count as healing to nearby targets (and healing as damage). I have that on all 5 toons. When activated in a burst situation the tank is really unkillable. The treants are also fun to use, 3 for tanking, 9 for damage and some little heals as well. All in all I see progress with my boss killings, but I seem to advance slower than other people in the forum. I really think that is my lack of skill though