Wonder Man at his strongest did well HTH against original Thor until Thor really unleashed the power of his hammer to finish the fight. And Herc has no hammer.
WM at his peak also had self-generated flight power, his ionic body was extremely durable, and he didn't tire or need to eat or breath (I can't remember if Herc has to breath but given that Thor does...)
So Herc could have a fight on his hands. For example if the environment allowed WM to fly Herc into space or drag him underwater Herc could be in trouble from the breathing bit.
Current WM would lose badly.