LMAO Of course it is bad news. You do realize, that the block time is supposed to be 120 seconds? Right now it's 26 second, it peaked at 17 seconds. So as long as they are there you'll find a lot of block in very little time. After they leave, well.. Your miners won't see any blocks in days (a week possibly?) depending on how long these guys enjoy their time in the pool. I hope this helped.
Eh that sytes pool been the main one I've used these past few weeks, and after the nicehashers or whoever leave, it'll be fine. Pool hashrate seems to be around 200 kH/s, and intermittently like 30 kH/s... Which just means a block per every ~5-10 mins, or hour-ish at the 30 kH/s.