Somebody does not have to get the boot. Delta could have contacted affected passengers and offered them alternative accommodations on other flights. It would be understandable if the downgrade was last minute due to mx, but when it occurs weeks in advance it should have been handled better and it is yet another total failure of customer service.

OP: I would absolutely insist on the refund of the mileage difference and then some in addition to way more than $200 in vouchers. Keep escalating the complaint. When enough people refuse to put up with this s**t maybe it will change.