I didn't specifically choose a Bard; the idea is to be able to fight effectively as a hero on my own. For this, I need Nature as a replacement for an army and a lot of experience to upgrade everything necessary. Stealth allows me to constantly accumulate experience, even if I can't kill these monsters yet, plus I steal mines, artifacts, chests with the same experience, and other objects that enhance the hero. For example, we're playing together, and right now, I'm 10 levels ahead, and without fighting, I have characteristics much higher than the second player with GM battles. I'm also equipped with powerful artifacts, like a bow with +50 to attack or a tiger set that gives regeneration and constant dragon strength, which I wouldn't have achieved without stealth. In general, the class is currently intermediate and will still change later, so it adds something, and that's fine.
I don't upgrade resistance because it's five unnecessary skills, and there's still a lot to learn. Also, magic resistance isn't required in every battle and can be easily replaced with antimagic if needed.
Melee and ranged combat may not be necessary in themselves, but they are needed to upgrade combat, which greatly increases survivability, and this is relevant for a solo hero.
I don't take a Demonologist because I won't be able to support this class, as I don't need Necromancy, and due to the upgraded Tactics, the class will be combined with it. And without a bonus to summoning, a Demonologist isn't very useful.

As for Liches and Vampires, you're saying something strange. You've already been told that undead and vampirism are not the same thing. A Lich is simply undead, and a Vampire is undead possessing vampirism. Depriving it of this is stupid; it contradicts the very logic of this unit, just as it's stupid to give all undead vampirism. Should skeletons also be vampires just because they are undead?