Volibear has yet to be perfected, yet i have found a build that seems to ravage the enemy team. Volibear seems to be an extraordinary tank and significant burst and when in ultimate, mass AoE dps.
Unfortunately I don't have time to finish this, it will be edited to a guide so please check back often. Any change suggestions please post in comments rather than knocking the build provided.

Also a few notes:
Your Q, is one of the best initiating skills. be hesitant to engage using it, it has a short CD.
Typical combo to get a runner is, Ghost, Q, E, W.

Passive is great. As you become close to activate your passive, begin to disengage until you have reached a comfortable level of health.

Any way that's all for now, please rate, and comment. Enjoy Mauling your foes with Lightening.