Other ways to get to SYD on DL miles would include China Airlines of Emirates. These may require double awards, but if you're looking to go to Australia and (a) avoid KE and (b) use DL miles, these are viable options.

While hunting around in DL's award tables, I saw the SQ 100,000 F award from US to Europe (primarily AMS, FRA). For someone considering a 90,000 J award on DL to either of these cities, they'd be wise to at least enquire about the 10,000 extra for SQ F. SQ F does have very limited availability, but, unless you're flying private, SQ is the best way to go.