I've never seen the need for a diffuser in my UDS, with anything I've cooked. I like the fact that the drippings fall into the coals and flavor the meat, and I usually cook my ribs in the 275* range until they're done using the bend test. I also "peek" once in a while to spritz with beer or apple juice. Leftovers are a rare thing round my house.
"Hey careful man there's a beverage here!!!"