In other words do you want to say that the hashrate shown by miner is utterly worthless?
Under such conditions the pool fee is whatever the pool desires and miners have actually no way of telling how much it is, regardless of what the pool officially says it is.

I was having another rig with 5x 1080ti and single 1070 on this zcoin pool for most of the april (few weeks). The awesome miner reported 16.5 MH/s while the graphs on MPH showed up to 12.
I don't think this is normal.
Is there anything I could check, e.g. network stability and latency ? I could set up some simple monitoring test over a week to see whether latency is too high or some TCP packets drops happen from time to time. I was calm until now because I saw 100% accepted in awesome miner, but I'm not sure I can trust this indicator anymore.

IMHO more then 10% difference sounds too much, 30% is unbelievable.
Could you please elaborate on the difference between "accepted by the pool" and the "accepted" as shown by awesome miner?

sure:
https://mega.nz/#!y7hxnDxT!-7xadc4E-0VkSWXFe4EmZtN72OW1z5gLJ6cvTIQIP-g

Mining zcoin with single GTX 1080ti 11G on miningpoolhub.com using awesome miner v4.7.4 which uses ccminer 2.2.5 cuda9. OS is Win10pro 64bit with latest patches.

ccminer claims the hashrate of 3200 kH/s in the console.
miningpoolhub shows accepted hashrate in the graphs for Zcoin under 2600 kH/s all the time. with average probably around 2100 kH/s

This discrepancy is huge and it's over a long period (few weeks). any ideas what is wrong?