Here's a hint if you are having a hard time reaching a US Delta agent that knows what they are doing: call the Delta Japan, Hong Kong, Singapore, Malaysia or other such numbers (yes, you'll pay for LD... but it may be worth the saved time and frustration). From my experience, the agents there know the Asian airline partners well (well, they have to, as presumably they do quite a few of such award bookings, given that now online none are no longer possible (KE, CZ, MU, etc. used to be online bookable), and also as they are pm-NW and thus better trained than pm-DL agents you'll usually get by calling the US #).

For example, if trying to book an MH flight, call the DL Malaysia res. #. Surely the agents there (not sure if local or goes through to Singapore) would know that MH is a partner.

The list of the #s is here: http://www.delta.com/help/contact_us/reservations/asia/