Yep its not only possible i have done it. I only needed 3 riveves and one of those was at the area before vanaduke.
The hardest part is ofcourse his 6 stage and even in solo i needed to do 3 douses with water and then full attack combos to bring him down. After that its a cakewalk. And i died twice only here in the 6 stage.
Next time i am gonna record it for proof :3.
Yea i managed to do that in the 1 and 2 shooting phase, but sadly in the third which would be the most important i killed him right when he changes. And could get the water fast enaugh
Ha, Ezero is the Vanaduke solo-ing champ. He was the first person to solo Vanaduke when he reappeared last month and solo'd him every other day for the first week. I came in second due to an ill timed bathroom break resulting in an idle out while my character was on the ground. /cry
Solo-ing him can be much easier unless you have good teammates, otherwise you loose more health to handing out revives than you do Vanaduke.
So... who's third? Me? ^^v Bleh I'm just kidding sort of. It is a lot easier soloing or duoing because you do tend to use up a lot more hp. For the Phase 6 shooting part, your best strategy is to use the water when he is so close, the outer most red orb can't shoot you so you'll have less to focus on. If you stay on the very left, you might notice a pattern where it'll indicate that the next time the outer most orb passes, it'll be behind the wall, that is when there's a good opening to throw the water.
Though I have to admit, I'm really bad/unlucky with phase 7. (Those evil dashes, it's hard enough to keep track of those orbs with such a crappy camera =/)
There was a trick that d0gr0ck showed me when he, Icarus, Njthug and myself went up against Vanaduke: when he just sits down to change into his bullet phase -- or when the screen changes view -- plaster him with a water ball. This is before there are any huge amounts of bullets flying around and makes for an easy starting combo.