have you disable the crossfire?
Weird,i flashed 4 cards independtly with modded bios,got 30 mh on everyone,then put all 4 working together,got one 30 and rest 27.5-28 max,same values on freq/voltages/power limit.
Now yes,all 4 do now 30 MH at nicely 77W in GPU-Z.
I suppose i can gain 2 Mh from super tuning ram latency but i lack the time to debug hex code and Heliox is rather on bragging but sharing so i kindly ask The Stilt to make light on this matter and help us all with his great knowledge.