from the manual:
[IMG]http://i.imgur.com/ZLCzKEx.jpg[/IMG]
DVI cannot be used while mDP2 is used. So supposedly that is the only limitation.
I have been on the line with gigabyte support several times. they are going to be testing the configuration.
Support # for gigabyte is is 626 854 9338 (then # 3 for tech) The technician is Ching who was assisting me. He told me they will be directly testing the configuration with this mobo and passive adapters. They were sort of dumbfounded that it did not work as well.
I think the bottom line is what drlarsen has been saying all along. Its a clock issue. HD4000 has 2 clocks but you should be able to put duplicate monitors on one clock.
I went ahead and ordered an active adapter, it was 20 bucks. not a bad price to pay, but the headache cost much more. Any plain person would just expect that if a chip and mobo both say "supports 3 displays" that it should work, regardless of connection type.