Disclaimer: my ger sucks (just hit 80 with the last two 1.5 weeks ago) but it's getting better.

I run 5 druids currently: 1 tank/moonkin, 4 healer/moonkin dual specs.

4 resto druids wasn't as fun as I was expected. I still died pretty damn easily and I couldn't really kill much. It felt like I was just running around spamming HoTs until a couple horde decided to take me out. However, this could definitely be due to my gear and if I actually had 600+ resil it's possible that it would be a force that's very difficult to kill.

Moonkins, on the other hand, are pretty damn fun even with shitty gear. Putting 10 HoTs on a target is enough to make them shit their pants. I dont' even know why I do that since one starfire round will make the HoTs never tick more than once, but I like seeing their debuff list skyrocket. Typhoon is your friend... it gets those guys off you and does some nice damage at the same time. You have a ton of healing power when you need it, though you're missing the AoE heal the resto druids love (wild growth).

I will try 4 restos again someday just for fun. I caught more crap from others in EoTS when they found out I was resto, whereas when I'm moonkin 80% of the time they enjoy me being there (unless we're losing, in which case I get all the blame, regardless of if I'm capping all the towers myself). I think 4 restos would really shine in a premade where you can go around with two warriors who just demolish everything. In a PUG I think you're often left healing people who can't do the killing that you would if you were just moonkins.