As we know druids are the spirits that we saw in the "WILDS"(those tranparent tree like creatures) in the game, but on what I know about druids are people (human and elves) that maintains the balance of nature. they have the power to communicate w/ animals and nature itself. the skills i have in mind for the druid is like a combination of ranger and elementalist (some are like from other classe too

here are some my ideas for druid skills.
Insect Plague - insect plague the enemies for confusion
Healing Circle - heals party w/ in the circle
Creeping vines - grabs enemy and deals damage of XXX for 5 sec
Tremor - earthshake
Elemental Barrier - defense against elemental attacks (like 10%+ defense against fire, water, etc)
Neutralize Poison - cures poison
Vipers kiss - poisons the enemy
Conjure Animals - summon aNIMALS TO FIGHT W/ YOU
Animal Rage - berserk mode in melee
Regeneration - lifepoints regenerates
Wooden Skin - +5 armor for a certain amount of time
Spider web - slows down enemies
Rust Armor - weakens armor
Animal tranformation - transform to animal form
flame and ice blade - damage of weapon becomes elemental( fire dmg, ice dmg)
some of the spells may make the druid class invicible, but if we put limit to it and put just the right amount damage to it, i think it''ll be fine.
you can observe that some spells are like from the other classes. but these are just suggestions that came into mind.