That's how the Dev fee works. Claymore replaces your wallet with his and mines for 36 seconds every hour. You should have asked Dwarfpool the time and duration of when the wallets were switched and compared it to the miner logs.
I know that is how the DEV fee works, However that is not the case as Claymore does not mine at 80mh's when he could mine at my full speed, Also when It is mining at that speed in the logs its not the DEV fee mining and the miner stops, then starts the DEV fee with his wallet.
The speed reported on the pool is also a calculated speed based on the frequency of the valid shares you submit, not the hash rate reported in the miner. It varies depending on share difficulty, stale shares, invalid shares and your latency to the pool. Sometimes it's lower or higher than your reported hash rate. On average it should be close to your reported hash rate.