Well, I'm playing with luck -3 all the time lately and total number of special heroes I've got is exactly 0! So I would say that luck scales have effect in Dom II.
As far as new heroes is concerned, since you have new nations its logical they will have new heroes. Old ones seem to have all those from Dom I (maybe changed a little) and probably few new ones, but I not 100% sure because of -3 luck scales (
) and the fact I haven't played Dom I enough to compare.