I’ve already told you how to deal with some of the things in Ruby, but your response was “But my dots”.
Quite frankly, that dungeon should feel terrible for you, as not purging something that will kill people is no different than not interrupting something that will kill people.
It’s entirely on you if you refuse to do the mechanics, and your silly excuse of “This wasn’t a mechanic in previous expansions” doesn’t hold water… maybe the exact mechanic wasn’t a thing, but we’ve still been purging shields and buffs on mobs for years now. You refusing to do so because of your dot uptime is a you issue.
This is why people like me never gets anywhere white knights, defending overturned dungeons and decliners on 20+ dungeons ive done yet they only take 2700 rated people, this season is worst season of m+ ive yet to play.
Not wanting to wade into the rest of this post. Final boss on tyrannical still does frankly cruel levels of damage with flamespit. Rest of the key is fine, but the last boss scales out of control a lot faster than other mythic+ bosses as key level increases.