Phase 1-Option one-Player 1 keeps shivering/shocking Vanaduke while the other slashes/guns. One bumps zombies.
Phase 1-Option two-Both players hack and slash OR gun OR One guns one slashes. One bumps zombies.
Phase 2-Both Players grab a water orb. Player 1 throws orb at mask, player 1 ONLY attacks. Player 1 goes back to go grab orb when player 2 throws orb and attacks. Repeat until Phase 3.
Phase 3-You can TRY to bug him although it is not needed. One player shivers while the other guns. OR both players gun.
Phase 4-Same thing as phase 2 although you can only get one orb while the other player keeps charging then attacking.
Phase 5-Try to bug if you wish, still not needed. Gun him in this stage, you may use shiver if you wish. Keep attacking until dead.
Hope this helped! If you wish for my help send me a mail regarding Vanaduke. IGN Bigfootm
YOU DO NOT HAVE TO BUMP THE ZOMBIES BUT IT MAKES THE FIGHT EASIER.
It's really a lot more time efficient for anything smaller than a trio to cut out the shiv spam altogether and just use some basic dodging. As it is right now, Vanaduke is slow and easy to predict and juke. Even without shiv, a competent solo/duo shouldn't have to energy res at all on a typical run. For a trio or full party though, I can understand how shiv can make things much simpler, especially since the loss of a single party member's DPS isn't as much of a hit to the party's overall DPS.
Sorry, just a little off topic tirade on all the shivving that's been going on. :)
(P.S. OOO, just make Vanaduke immune to status effects and/or increase his turning speed)