The raid DPS requirement are indicative, nothing in the game is that clear decided. Statistics always lie in a way or another and that why parse and such are tool you use for yourself, not something that could tell how anyone should play.

Lining up numbers menas nothing by itself, the only thing that matters in that specific case is "did the boss enrage". If it did more DPS is required.
You can use a parse to try out what does more and what doesn't, but it all comes down to what you do in the game, not some abstract number ceiling. R-DPS also kind makes every one forget that the boss have an HP bar. It dies because its HP reach 0, not because R-DPS is 23k for 12 minutes. And this illustrate why "throwing a DPS spell is always a gain" much better than you ever did all your hundred of post on how healer DPS is a necessity.

Basically "DPS all doing 4.5 DPS" doesn't even exist in the game, it's specific abstract reasoning tailored to get to a concrete conclusion. Wich makes your reasoning false even though the conclusion isn't. Because the same abstract reasoning could lead to "better team composition leads to better R-DPS".