So her hero power is the same as heroic Kel’thuzad minus target hero only? Yup, totally not OP.  

@PonyPon  
I think she’d probably be similar to an upper (but probably not top) tier human mage in overall capability. She hasn’t shown as much battle magic as they tend to utilize, but she’s got significant tricks that only the best mages in WoW can pull off alone (like teleportation and telekinesis that can lift thousands of tons).
 
If I had to pick someone that I thought was close to her, I think maybe Jaina (WCIII era) might be a good pick.

@PonyPon  
True, especially when we only consider legendary worthy mages. Unless she wields the power of four alicorns, then she’s pretty good. She’s also quite capable at telekinesis; something you don’t see often from Warcraft mages, but when the most powerful of Warcraft mages act in unison, they can make a whole city fly

Have you seen any of the mages in Warcraft, human or otherwise, Op?
 
Twi is small potatoes to pretty much all of them.

SIX MANA?! I guess the hero power and weapon aren’t quite as OP as Jaraxxus, but 6 mana? Should be 8 or something, I feel. Especially as a neutral.