Yeah as you say maybe its too much for a program like Premiere to handle as its for realtime editing. Its a shame though as it creates an extra step in the workflow. What I have been doing is creating flat images from the DNGs so they are more like v-log footage, that way I can still do all my color grading in Premiere where I get instant results, as apposed to having to render everything in After Effects. I know this kind of sounds backward by using RAW and then flattening it, but my Canon EOS 7D cannot record good quality video unless I use Magic Lantern and record RAW. If I had something like a GH4 then I would obviously record as V-Log footage in the first place.