FWIW, DOT guidelines are around a drop test so they are pretty much useless unless something falls straight down on your head or you flip over and land head down. Neither or which are likely to happen. I would avoid any helmet that is just trying to meet that standard and has no other safety testing involved.
Where are you getting your information from? post your sources that give DOT's guidelines and how they do their testing. I doubt there are many helmet manufacturers that overly exceed what the DOT requires.