Cheep valve covers with no baffle:
Valve covers angle a bit to the rear of the engine oil sprays and splashes off the rockers and hits the top of the valve covers runs back to the grommet runs down the sides of the rubber runs off in a stream or hangs in droplets on the end of the grommet and is sucked up by the pcv, the baffle acts like a dam around the grommet it stops splash and the oil running down the top of the valve cover to the rear of the engine before it hits the grommet and it runs dawn the side of the baffle and drops off Keeping the grommet fairly dry!! Blow by can push oil into the baffle and breathers or cheep set ups will be in the oil stream off the rockers like F.B. said! I doubt if you have excessive blow by! You just need valve covers with well designed baffles
Some valve covers have windage dams above the rockers and stop the running of oil along the top of the valve cover and direct the oil away! Cheep rocker covers just look good and even the baffles don't do the job they are intended to do!