I have been mining Zen on supernova and have noticed a really irritating trend from large miners.

When there is a period of bad luck - the last few blocks are a few hundred percent over the estimated solve time then statistically the next few blocks will be solved under the estimated solve time.

These guys smash into the pool massively diluting the payout for the other miners for the blocks that will be solved in a far shorter time and then leave again, most of the time they do not even solve the blocks.

It really screws up your earnings because if you have had 1 hour of bad luck the 1 hour of good luck and you are getting far less thanks to the large miners so the total average is much less.

Most of them have hash rates so high they could mine solo and still earn 300+ zen a day.