Captain Panda
Explorer
Their level 6 spells are a tiny bit weak compared to other spellcasters, so you could argue that they fall behind a little bit at levels 11 and 12... except that their overall package is still great at those levels.
The one weakness of Moon Druids is that they have no organic ranged combat capability. They pretty much always have to close with the enemy (in person or via summoned proxies) in order to destroy them. So in a campaign which consisted entirely of fighting dragons in flight, Moon Druids would be a weak(ish) choice.
Call lightning isn't great burst, but it is solid sustained damage over time at range. Same for sunbeam. They aren't perfect options, but they're something. If a dragon comes and opts to never land, the druid still has options. If nothing else, he can just turn into an air elemental, fly up and punch the dragon in the nose.
Druids scale in power in a very odd way compared to other classes, with huge spikes of power and then slow declines, followed by another spike and decline. That said, even at their lower points, they're still always a very good choice to bring along. They have weaknesses, but suggesting that a cleric is better than the noble druid is laughable.