Use Discharge ( a-a-s ) and Vent the Steam ( a-h-a I think? ). The first will remove his electrical charge granted by the undead mages. The second will spawn a big cloud around him, leading to an easy stun every time someone tries to electrify / supercharge him. Basically he won't act from the entire fight if done right.
Last edited by Dr Koin; 12/11/15 07:52 PM.