I will say that Druid is the class I tailor most for my campaign world ... and I do so to give it a more defined role.
In my setting, Divine, Arcane and Nature magic are all delivered through the Weave. The Arcane is taken, the Divine is sent, but Nature is accepted as if drinking directly from the stream rather than grabbing it in a bucket or having someone deliver it.
the weave begins at the heart of the Positive Energy Plane and flows through everything and into the Heart of the Negative Energy Plane. It is life and death as a continuity. As the spellcasters most in touch with this conduit, druids in my setting are devoted to maintaining the conduit through balance, and also capitalize on both ends of the spectrum. To that end, I have a few homebrew subclasses for druid that tie into death, reaping and even undeath (in an anti-paladin sort of way). I also added a number of death and necrotic energy related spells to their list.
My druid organizations are mostly devoted to using the natural flow of magic to preserve the Weave. That generally means ending things like undead that disrupt the weave. That means preserving life forces within regions by keeping nature healthy. Some are founded in dark times and exist only to support the Light ... while others originate during positive times and seek to dampen the light to maintain balance. Other druids are not beholden to any organization or creed - they just figure out how to tap into the magic and use it for their own ends. They generally damage the weave and become foes of the druid organizations that support the balance.
I find that does a lot to balance the class and give PCs specific ideas of how their PCs might fit into the world.