If you don't get impaled, it's actually a good time to heal or cast buffs since the animation is pretty long and you can't hurt him anyway. Even long cast ones like replenishment can be activated safely right next to him. You still have to be careful though, one of the patches seems to have made him (purposefully or accidentally) more unstable, he cancels his attacks all the time now. I saw one recently where he seemed to lightning stab somebody, only to cancel it and go immediately into the drop down portion of his lightning butt slam instead. Basically went from stabbing the guy to falling from the sky onto his head like some sort of evil combo move. It ended poorly.