Well, that isn't actually the complaint. At least, it isn't mine. He has no non-combat *abilities*. Teleport, create undead, invisibility, magic circle, all that stuff. Poof. Gone. He's an immortal being with nothing to do when he isn't killing people.
On the skill side. Maybe a 3e bard. But a 15th level bard with an 18 Charisma would come in at a grand total of 7+4+5 (+16) on his trained skills.
Except for trained skills, he has the exact same skill bonuses that anyone else of that level would have with those stats. Maybe they'd train a different set of 4 skills. But really, he's using any skill with more or less the same proficiency as anyone else who could be viably compared to him. Unless they have some large bonuses he doesn't, its just a random die roll.