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LOL! Cleric of Velsharoon / Wízard / True Necromancer / Draegloth? I can't think of any combination this unlikely to happen. Since Draegloths are supposedly born with influence from Lloth, I doubt she would like Velsharoon stealing her worshipper. Attempt to explain how this could have happened is so weak. Not only that, but add wizard...just forget it.
In order to be a True Necromancer you must have levels of both an arcane spellcasting class (IE wizard) and a divine spellcasting class (IE cleric). I see nothing at all wrong with this character.