He's already dead, but here's a thread anyway! For anyone that wasn't in the fight or didn't understand what was going on. Also for future Heroic discussion!
One Very Important Note: Common wisdom, such as in the Icy Veins guide, is to put a raid marker on the Arcing Smash areas AFTER each cast. The raid then moves to an area with NO mark for the Breath. We did it differently. Suggested by Swipe and Hobugz from a Flex raid they did, we put four marks out BEFORE the fight starts. North, South, East, West. Then we paid attention to where each Smash hit and had the raid move to the mark that was safe. This was substantially easier for me to not need to toss marks down and clear them during the fight. It was also easier to direct and I imagine easier to follow. "Go to Blue" is easier than "Avoid Purple, Green and Yellow."