So we missed an entire difficulty level... The entire time network difficulty was 2603B (from Jan 22 to Feb 6) we did not find a block... Has that ever happened before?
I hate to say it, but we might be getting too small... I can accept variance, but at what point is it too high?
The answer is "what ever fits into your comfort level", pure and simple. I'm fine with it.
Been here for years, variance will be high with 50Ph, but I see the issue as lost fees, for a while we had crazy high transaction fees (3-9 BTC Fees) so not finding blocks during those times hurts overall rewards. In the end its always 100% but missing bocks at those crazy high fee times hurts...
Just saying....