I have had the same issue with OverdriveNToll and Claymore.  I can even watch the cclocks and mclocks in HiWinFo64 change, but there is no change in hashrate until I restart the rig.  For me, this problem developed suddenly and was not present when I first built the rig.  Indeed, this does make optimizing a card a real pain.  What kind of cards are you running?  It happens to me with RX580s with Elpida memory (blockchain drivers) on Windows 10 using Claymore 10.3.