Very easy battle, open with conventional stunlock, he will trinket out and roots, trinket/vanish out of roots/bash, keep sprint up, should be running crippling main, wound poison offhand. The druid has zero survivability in caster form, but should this druid be keen on bear form, which he should be, then a 5 point EA is advisable on the opener, on frenzied regen keep s&d up as you will have excess points - it will take a while to bring down.
Any time he switches to caster, kidney shot him, hit sprint, make sure you have not blown any of your vanishes. As soon as you see a switch to cheetah, hit blind and sprint. In my experience, this is a very easy battle.