Guardian

A ferocious bear that wields the brutality of nature and claws to survive large amounts of damage. Very little can get through a guardian druid’s thick hide, and whatever does can be healed with nature magic.

 

An extremely useful tool for overall optimization

http://www.askmrrobot.com

WoWhead Guardian guide

http://www.wowhead.com/guardian-druid-guide

Icy Veins Guardian guide

https://www.icy-veins.com/wow/guardian-druid-pve-tank-guide

Noxxic Guardian guide

http://www.noxxic.com/wow/pve/druid/guardian/