I've also noticed that the reported hashrate varies by quite a bit. Is this calculated based on actual results or something else? Here's an example:
To my understanding, variance is and should be happening only on x16r and x16rt since the used algos vary, for others just the order changes so it should be stable
Lets say it takes 10ms to calculate a slow algo and 1ms a fast one, so if you do slow first then the fast one, its 10 + 1 = 11ms
And if the order is reversed then its 1 + 10 = 11ms again... Just that you eventually do it with more algos.
x16r and x16rt the algos used are random (from a given set) so it varies, but for example x16s, its same algos but different order, so it remains stable
maybe I miss something, but this logic supports my own experience mining them