sampires are kinda built to go solo. and often if others are in the area they will mess up the sampire. imagine fighting rikky as a solo samp, he stays where he should. now other people are drawing aggro, he's running around killing them, they're all oOoOoOooing...
a good partner would prolly be a stealthing/discording/mage/myst justice combo
disco to make the boss easy, myst for cleansing winds, stealth to stay out of support, and mage to curse and for support