I think Melissa is a fine name for a sorceress, eg 'Melissa Ravenflame' is a classic Sorceress name. Whether David is a good name for a minotaur depends on the campaign - to me the name has a religious Old-Testament sound. It would be good for a minotaur Paladin, say.
IMC Robert would be a typical name for a particular region (the Northwoods, similar to medieval England) but not for some others. BTW Stephen seems a very common name on Mystara - lots of Stephens, Stephans etc there.
