I booked our Asia trip on February 8 for traveling in December for family of 4, low level business class:
LAX-CAN CZ
CAN-KIX CZ (stopover)
NRT-TPE BR (using UA, destination)
TPE-CAN CI
CAN-LAX CZ
It was a VERY difficult task and I took off work and spent ALL day on the phone with DL. I had to give up on DL for NRT-TPE segment because DL couldn't find availability. What's weird about that leg is EF shows 2 in business and 4 in economy. When the phone rep did a long sell for 2 business and 2 economy while I'm constantly refreshing my EF page, I can see the inventory in EF go down respective to the seats I've request but within a minute, DL rep will come back with no availability while EF inventory will show the decreased inventory. At first I thought the seats were taken by another customer trying to book the exact same thing as me, but the inventory would come back to 2 business and 4 economy on the top of the following hour. I would call again and same thing happened; in fact it happened three times, three hours in a roll. So I'm confident that I have caused the decrease in EF's inventory, but somehow DL can't book it ...I'm confident to say that the reps I talked to knew how to book CZ because they knew how to get the other CZ segments. FRUSTRATING.
By the way, DL had great availability on DL.dum if I was traveling alone....they had ONE seat at low level everyday around my outbound date and for all the segment I need to go to Japan and Taiwan, but Just ONE seat per day...ridiculous! In the bright side, I get to try the A380 :-)
Another note, I was grateful that UA allows one-way redemption and provide lots of availability for family if 4. It literally took me less than ten minutes for me to book NRT-TPE and only 20,000 miles / person for business class. Good luck!