Don't know why we didn't see this before..
...
However, in looking at it again, how much compression is done between the dmg file and a .pkg file? Because that is what is listed as the combo update in the 1st link, which also wouldn't have included the firmware update. My guess is that whatever little space for compression/compacting that goes into the .dmg wouldn't allot for the Firmware update, so they should even out.
BL.
If we compare delta updates the size does nicely match (there's just 1 242 885 B difference):
1. DMG
osxupd10.11.4.dmg: 1 580 282 462 B
2. PKG
OSXUpd10.11.4.pkg + FirmwareUpdate.pkg: 1 453 682 103 + 125 357 474 = 1 579 039 577 B
While with combo updates we're way off (361 885 287 B difference):
1. DMG
osxupdcombo10.11.4.dmg: 1 942 964 664 B
2. PKG
OSXUpdCombo10.11.4Auto.pkg + FirmwareUpdate.pkg: 1 455 721 906 + 125 357 471 = 1 581 079 377 B
That's pretty big difference given that there's practically none in the case of delta updates. Some compression? Maybe, but then why it's ineffective for the delta update? More thorough comparison would be needed, then we may get some idea why there's such big difference. I've already deleted the pkg and don't want to download it via my current mobile connection, but may try to download it tomorrow, extract with Pacifist and compare the contents.
Yeah, I used:
https://support.apple.com/kb/DL1869?viewlocale=en_US&locale=en_US
With the firmware update included in the bundle. Worked fine, the download took 1 1/2 hours though.
Yeah, if swupdate download keeps stalling, try this one. It downloaded much faster for me as well.
I think that Apple should really reconsider their release publishing planning. When they do it like now - that means all OS X, iOS, tvOS etc... updates go out at the same time - they cause major spikes in the content delivery infrastructure utilization. Some staged approach would be better.