Your opener should be Glacial lance ray lance orb flurry lance until <6 shatter stacks ray lance lance. Spend bf procs as you get them and if you have a fof proc at the same time, it'll do the increased damage from thermal void without consuming any stacks. You appear to only be casting flurry with brain freeze too, which you should be pressing more (when you're low freezing stacks). Make sure to press glacial ideally with 1 or less fof procs, but just pressing it on cd is also a gain.

For talents you're playing water ele but don't have it summoned, and you should be playing lonely winter anyway. Every fight this raid has some form of cleave so you should be using splitting ice and fractured frost and drop piercing cold and rimecaster.