Never ending invisibility, ignoring Mage light detection. Recharging way too fast and allowing to re cast it without going out of invisibility. On top of that Bolt Escape work while invisible like its not enough already. Should have no place in pvp system.
And example on vid its not even emperor, we have those abusing it also in campaign.

https://www.youtube.com/watch?v=mKpitGvO-ME&feature=youtu.be