I think there are 2 possible ways to play a druid solo: melee tank and pure caster. Druid has the best base tanking stats out of casters (apart from chanter which i consider only 50% caster), and better than a rogue or probably even barb since extra deflection > health. He also has nice self heals.
For pure caster approach wood elf/moon are pretty obvious. I'd say moon is less valuable for druids since they have decent healing spells, but it's good it any case. For stats Int, Might, Dex in that order, Con/Per - dump as usual.
For tank you still need Int and Might but I would dump Dex and transfer it into Res/Per/Con. Con is still pretty bad as a stat but fortitude is pretty important. Good tank races as usual are Pale elf/Moonlike/Wild orlan/Aumaua. Pale elf druid will have the least problems with shades, wild orlan is good for dragon/vithrack fights and moon is just good all around. Aumaua is probably the weakest option, but still decent. You can also still go wood elf since you're going to be at range anyway some times.
Fast runner is a must have for ranged and still a consideration for melee. Deep pockets is awesome for anyone solo, probably the best talent you can pick for harder fights.
Some thoughts on druid spellbook: Druids have straight up nukes, DoTs, lasting damaging effects like returning strom, summons, heals and some buffs, mostly defensive ones, and some debuffs/CC, often mixed up with damage. Straight up nukes are only good for caster as you want to spam them fast. Tank variant can still use one as an opener. DoTs and lasting effects naturally synergize with tank approach since you cast them once and they deal significant damage over time (while you can tank).
Main weak points of the druid are cast speed (use aclaricity potions for hard battles - deep pockets!) and accuracy (no inherent way to boost it unlike all other casters).
The most potent spells from my experience are returning/relentless storm and earth talon (petrify vs reflex!). It is possible to stunlock enemies indefinitely with storm spells and int > 20. You want accuracy boosts though (when it lands it gives -30 reflex so subsequent hits are MUCH easier, but you need to at least consistently graze first). Reflex being the weak save of many tough mobs helps.
For what it's worth I was able to solo the Adra Dragon using a test druid permanently stunlocking her with storm :D.
Best shape is probably Cat as it has the highest DPS. Some arguments can be made for Bear, as it has more DT. Wolf is an option for a ranged caster because it gives you move speed so you can run away (shift is instant). It might be even able to replace fast runner (haven't tested). Forms go out of fashion as an offensive form pretty fast, but are quite decent at the start of the game.
Edited by MadDemiurg, 30 April 2015 - 09:12 AM.