You seem REALLY confused about what you are even arguing. And since you are claiming your statements are objective, you will easily be able to support your claims with evidence. Your issue comes from A) thinking your personal opinion is a verifiable fact. B) Applying one standard to the negative, and an entirely different standard to the affirmative; You say firelands only having 8 bosses was a negative, and yet dont say the same about DS? and C) You genuinely dont know what you are debating - the context was DS being "objectively better" than firelands, and yet to try and quantify that, you need to compare Firelands to the previous tier.....
Thats like saying Return of the Jedi is a better movie than Empire strikes back, because Empire strikes back isnt as good as A New Hope.