The periods you mention, with Dorfman and earlier Bates around 400 and then the following stretch with those excellent Cardy covers and the neat trade dress, are treasures to me. Action 421 is just one of my favorite comics, but I don't have Action 422. My lcs has it and for some reason I didn't pick it after skimming. I'll be there tomorrow and hopefully get it.
Currently from 393 to 422 I'm missing 405, 407, 419, and 422. I forgot why I ended up with two copies of 411 but it's good and I guess I can give one away if anyone wants.