Gridseed hashrate all over the place

I've got a couple of gridseeds clocked to 850 and I have tried them on all sorts of pools. The hashrate seems completely unstable varying wildly, including reporting hashrates as high as 450KH/s, but often as low as 250KH/s. Yet I am getting zero or close to zero rejected.

Is this just the way pools report the hashrate? Or is it actually that unstable?

LTCrabbit seems the most stable reporting hashrates 330-380 per hour. Clevermining reports wild fluctuations between 100-600 and ghash.io is fairly stable on LTC but completely wild on the multipool. On wafflepool it is very low and I seem to get very very low returns, although I tried it for less than a day.

So I am wondering if it all averages out and I am fine to use all these pools, or if actually I should avoid the unstable ones; I also notice on the unstable multipools a great deal of "Stratum detected new block" messages.

Any advice from you experts much appreciated