So ... Slushpool just cracked a 550% that took 8 hours ...
Get ready for influx of refugees boosting our hash rate!
BLOCK DANCE!
Not sure where you are looking, but Slush reports block % favorable. E.g. if they find a block in less than network difficulty, they count that as positive luck. So the 550% block, took them 15 mins, not 8hrs (not sure where this number is coming from I looked back through their block history and I couldn't find an 8 hour block anywhere in that last few days/week).
Easy to find:
https://slushpool.com/stats/blocks/?c=btc32986 2018-02-14 14:36 08:04:59 2.351 Eh/s 2874674234415 18.10 % 509115 12.80191632 BTC 52
18.10% luck block at Slushpool, roughly 550% difficulty block.
8 hours, meaning 6.5hrs of hash "wasted" based on their scoring.
Dunno why people don't complain more about Slush ...
Edit: I guess you're talking about their 571% Lucky block that took 15 minutes ... only takes off 1.5 hrs or so off their unlucky streak

Edit2: BLOCK BY COBRA! MINE ON!