I was googling Delta schedule change and came across this thread. It is amazing how clear Delta's CoC has become.
Anyway, I just got off the line with their international desk and refund dept. They refunded two non-refundable $6,240 business fare tickets because the return from SYD to PHL (via LAX and MSP) arrives at 908PM, instead of 708PM as originally scheduled. Fortunately for me the agt didn't notice the other 711PM arrival via LAX/DTW. Now I have a clean slate to purchase other tickets and avoid the $400 change penalty on the fare. Due to change of appointments I had to change the outbound anyway, which forces a reprice of the entire ticket. So if you ever have to make an expensive change, verify any sked change hasn't broken the 90 min rule.