And that hit still required a class who can do burst DPS on demand. During progression, not every class was capable of doing that. Afterwards, neither. I remember doing it during DS while farming a legendary, and the mage was fire, the hunter wasn't MM. Mechanics like these force people into playing a certain spec, and such mechanics favor 25m just like rogues on Spiritbinder are a great asset and are more common in a roster for 25m. I'm also not reminding you of FL, you brought up Beth yourself.
If 10m gives them better progress, yes!
Oh I understand that perfectly fine and as far as I'm concerned it is time to put the final nail on the coffin for 25m raiding. It simply doesn't scale unless you're a hardcore player, and putting such a large amount of development time in such a niche simply isn't worth the USD for Blizzard (and not worth my monthly 15 EUR tax either)
Due to this I believe switching to 15m is the best solution to the problem. The rest is just duct-tape (consumables etc are too minor to be relevant) or plain unfair to 10m (charms, extra loot, more mounts).