When I first implemented the stat delay, I immediatley changed the pool stats API to show the current round at 1 second with 100 shares. Within 15 minutes the pool speed increased over 200 GH/sec. We are still higher now than before I put in that delay.
That 200 GH/sec is likely all the pool hoppers thinking you found a block as your API reports that condition. So by your data hoppers account for about 8% of your pools peek hash rate. Report a round with a few hours and 1563027+ shares and those 200 GH/sec will prob disappear. I am not convinced that stat delay will solve the issue as there is already a published method to deal with deepbit's delay.