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.
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.