I remember reading somewhere that Strahd was a Wizard 16/Fighter 4, with Bastard Sword proficiency and a mess of other feats from the PHB.
I've played this adventure about a dozen times. Strahd has been a Wizard, a Wizard/Fighter, a Cleric, a JPM, an Alienist... But when I broke down and read the adventure, I noticed two thinks- first, Strahd usually just shows up for half a second to cast cloudkill, and two, Strahd hardly fights in melee. I had the idea of turning him into a Ultimate Magus... But I ended up changing him to a Necromancer 10/ Dungeon Lord 5 (from Dungeon Scape, a very fun prestige class). It certainly infuriated my PCs, not because he was powerful and dropped two players over time, but because they couldn't figure out for the life of them why every monster could open a door as a free action and they had to spend a move action.