Is getting 10% rejected shares normal on the multipool?

Miner sometimes says rejected share because difficulty too low, even though the difficulty was high enough (example 515/512)
Most people observe a reject rate of 4 - 7 %. Where is your rig located? If the pool continues to be that successful the developers plan to install an EU node.
Yeah, I'm located in the EU, so that might be it. EU node would be awesome.