With the big bang ability on Algalon not counting invulnerabilities. It is essentially required to have a shadow priest for big bang, otherwise you need to try extremely inconsistent strategies (elementals on shaman, tanks, etc). Almost every kill has a shadow priest. This is fine for 25 man, but on 10 man it is just kind of stupid to require a single spec of a single class. Does it really change anything to just allow bubble or iceblock to not cause the boss to kill the entire raid? Why not just change all invulnerabilities to work, it doesn’t really increase the difficulty of the fight and most of those are on long cooldowns. Glyphed shadowpriests can soak every single one themselves without any trouble, so why not just share this with other classes?