You have come full circle to the many benefits of having a parser. This is actually what it tends to be used for more often contrary to popular belief. Not only that, its VERY easy to single out WHERE players lose DPS like on what phase, and having this information allows players to adjust rotations or cooldown usage in prior phases.
Many who are against parsers, so far I have noticed in this thread, do not actually raid on current content (go figure). Why is this relevant though?
I feel there is a lack of understanding of what a DPS check really is to these people. None of the current EX Primals(Odin included) are valuable in this DPS environment as most that have enrage timers, are easily downed before them unless massive amounts of death come into play. Then you see something like Odin which seems different from most fights, which seems intense (even though his "DPS" check really occurs at the 15% rush, easily completed by holding buffs till then.)
Now imagine if you had a DPS check for the entire encounter that was actually rather strict, then mini DPS checks in-between certain phases (adds for example having to die before the next phase/ or usage of certain skill). Parsers help these moments greatly by seeing this information. We don't necessarily have the time to sift through everything in battle log, pull out a calculator, take some averages and see what were doing, granted most people I've raided with as I'm sure others still actually check battle log when "something" did a lot of damage to them to figure out what it was.
Yes it is possible that all of your DPS know their classes and how to play them very well and still fail a DPS check during a particular add phase mid encounter simply because they haven't adjusted their overall rotation to the encounter to better arm themselves for that particular phase. You may then say, "yeah but its obvious if you need more damage on add phase, save cooldowns for the add phase!!! Eureka!", yeah but are you forgetting the overall enrage thats still strict for the entire encounter? I may save buffs in the previous phase to go ham on the adds phase but is that helping us beat the overall enrage encounter? What if im sacrificing too much in the beginning, to burn down those adds and thus my beginning DPS is not very high? This is where parsers come in to better illuminate the entire picture. It can with frequency show you how much sacrifice is enough to do both.