DL Vacation count as "exception" MQD computation, it's mileage based not $
DL Vacations air itineraries
can count as "exception" fares when bulk airfare is used, but this is not guaranteed (sometimes bulk fares are not available and published fares are used). Generally, a travel agent can circumvent the issues you're having with the phone hold times, but if you already have vouchers from DL Vacations, you will have to deal with them directly to redeem.