Most werewolves are warriors, since the only way in skyrim to contract lycanthropy is through the Companions questline. However, as long as you slap Vilkas around with a sword a bit in your initiation, you can get into the companions as a pure mage, and never use weapons again. This character does so, rushing to the ability to transform into a werewolf, and eventually heading to Falkreath to do the Ill Met By Moonlight quest, gotten from talking to the grieving couple in Falkreath's graveyard. Help Sinding, and get the Ring of Hircine as your reward, allowing for unlimited werewolf transformations by reusing the ring's power. Doing the companions questline in its entirety is still worthwhile, as after its completion you can get the Totems of Hircine by doing quests for Aela the Huntress. Another useful quest is clearing out Frostfell Lighthouse and getting the Sailor's Repose perk.
The druid is a spellcaster focused on channeling the power of nature. She calls upon fire, ice, and lightning to ravage her foes. With alteration spells and mage armor perks, the druid is tankier than a normal mage. This is compounded by leveling health. The wildshape druid levels magicka and health about evenly. Focus on leveling magicka first, until you have a respectable amount, and then start adding to health so the werewolf form can keep up with stronger foes. Once you are comfortable with your level of health, go back to magicka. While you will have less magicka then a pure mage who leveled that exclusively, the wildshape druid can become a powerful melee character once drained of magicka, cleaning up anything that remains.
The wildshape druid is a high elf, because this build cares so much about both magicka and health, the 50 extra points in magicka are irreplaceable. Highborn is also a very strong racial power when combined with destruction dual casting and impact. Use the mage stone until you reach 100 alteration, at which point you can take the atronach perk and switch to the atronach stone. The spell absorption from these both apply while you're in werewolf form, making it even more resilient.
I found werewolf form especially useful against mages, who are annoying to fight as another mage, since they will block your spells with wards and drain your magicka with lightning spells. Werewolf form is also incredibly useful for traveling, having incredible stamina and unrivaled speed bounding through the wilderness. Alteration is the most useful skill for a werewolf, as any flesh spells you have cast carry over when you transform, making the werewolf have great defenses. The restoration perk Avoid Death is also useful as a way of healing for a werewolf. Lastly, if your magicka allows it, you can cast a destruction cloak before transforming, giving your werewolf an elemental aura of damage. This just looks cool more than anything.
The wildshape druid is a fun character for having access to two totally different playstyles at the same time, and each one complimenting the other. The humanoid side of the druid is a powerful pure mage who has mastered the natural elements, and can ravage enemies from afar and stagger with dualcasting destruction spells or incapacitate with paralysis spells. The bestial side of the druid gets a huge boost to health, can keep up high defense from alteration magic, and suddenly becomes fast and physically powerful, tearing through enemies in melee combat with savagery. With access to both, the wildshape druid is a force of nature that can take on the deadliest challenges in skyrim, adapting to each situation through the two forms.