??? 4 Str 4 attacks that ALWAYS strikes first, a 4++ save (regen), one of the best bound spells in the game, IMHO (2d6 Str4 hits, if a wound is caused, unit may not move in next movement phase), and a Smiting Incantation that is always cast as irresistable force. You really can't ignore the fact that this army, with Khalida as its general, can put out 126 poisoned arrow shots per turn, either. That's enough to take out 20+ lightly armoured models each turn, and even more importantly, its enough to weaken the enemy enough that the fear causers can outnumber them substantially.
Truthfully, I think that she may be a bit more expensive than her abilities warrant (considering the average cost of a Tomb King), especially since the Blessing of the Asp costs about as much as another large unit of Skellies. She does take a bit more finesse when playing, but I think she can be worth it. I'd probably not take her to a GT all the same. We'll see.