Static diff does not work and your vardiff algorithm is buggy, (for digibyte-skein) at least.

setting works, for a while and sets the difficulty at 1.536 and then vardiff kicks in and changes it.

vardiff keeps increasing the difficulty until the miner submits nothing for a a few minutes. After not submitting shares for a few minutes vardiff drops the difficulty a notch, and I can see 1-2 shares if it gets lucky, and then bumps up difficulty again -> no shares -> lower a notch -> 1-2 shares -> increase -> rinse and repeat.

in 2 hours of mining with same test hardware, the block factory earned 120 DGB while mining pool hub earned 14 DGB, this is fudged up. (Yes, 120 vs 14 it is not a typo)

In the test hardware there is a mix of 1080/1070/1060s and vardiff setting the difficulty to something over 8, even 1080(~1GH) cannot find a share. I'm curious what the vardiff algorithm is targeting for..