Just my opinion really but I would agree.  They do feel like a Mary Sue race.  I'd be using that race constantly for my sorceress' due to that ridiculous charisma adjustment.

However the race to me feels unclean.  Unnatural implies unicorns would kill them and druids hunt them.  Natural things die.  Natural things decompose, giving birth to news life.  To me this race sounds anti-nature.  Selfishly refusing to give back to the world that created them, forever refusing to return to the soil that created them.