It's evil, no question. But isn't it also kind of evil to steal source from people, dead or not? Most undeads I faced were evil, because they tried to kill me, and that's enough to make them evil for me. Lord Withermore however, whom I consider undead, was a nice guy.
To the healing problem: I think it's an interesting variation. I do not believe that it will make the game unplayable with an undead in the party, perhaps only more difficult. And different. And that's what different races are for in my opinion.
There is a bigger problem: undeads are ugly. Buuuh. So like dwarfs and lizards they are out of my party. Which is a pity, the gameplay sounds interesting with them.
