I see that many people here don't understand the miners table on Zpool and HashRefinery.
Under the miners table you see a "live" hashrate calculation based on your recent shares. That number WILL FLUCTUATE! It's normal.
You'll see a wild fluctuation depending on algorithm, ranging from 20% to 60%.
I'm constantly mining on these pools using profit switching with my in-house developed software. Nist5 and Neoscrypt are frequent algos we mine and I don't see any problem on the poolside.
Our scrypt miners report 200-800MH/s but they always average 550MH/s (slight overclocked, matches hashrate on miner side)
So it is normal, check the hashrate graph, not the live report, and if you mine for short periods It's like flipping a coin.
Typically I average ~ 650 mh/s for NIST5 however several times Hashrefinery would show 6 mh/s to kh/s for extended periods of time which is several magnitudes under the level of my current hash rate. Has done this over the last 24+ hours.
When looking at my graph, it looks like a saw tooth to be honest with 4 one hour periods of normal hash rate in the 450mh+ and seven two hour periods of basically no hash rate less than 10 mh/s.
The entire day I mined NIST5 so pool switching does't account for the behavior. I understand variance but something else is going on here.