When ICC first came out I was able to have a stacked proc ready for bone spikes but nowadays the dps has come up a bit and my procs can some times land on spikes with not enough health. I could just dps the boss but i'd rather show good dps on the boss and the spikes. I've glanced at a few log and seen some mages use blizzard and some dont. I've never tried using blizzard on this fight honestly. You could wait to proc your 2xT10 bonus and cast your blizzard. Have any other mages expericenced said dilemma?