I spent some time playing this morning..

I did notice that the difficulty rate varies wildly around every 5 or 6 seconds  shooting from a difficulty of around 9 to around 940 in some cases..  whilst the charts are showing reasonable rates, the gridseeds are jumping around all over the place on difficulty and the no of accepted blocks between new blocks being detected is awful.

I would suggest the difficulty is still changing too fast and is too inclined to go harder..  there was one period where 8 new blocks were detected before any of my 5 gridseed 5 chip units could get in an accepted share and during that time the difficulty jumped all over the place as the new blocks were detected.

Just my 0.02 mBTC worth.

Regards

M

oops EDIT...   it may be I was playing at the same time as you Terk..  let me leave it running a while and see what happens