Playing Skyrim again without upping the dragon difficulty is proving to be very hollow to me.

I guess I like a challenge when I fight against such massive lizardly time-ignoring beasts.

So, Deadly Dragons has no support for the DLC random dragons, and so do many others that I've looked up on the Nexus and Workshop.

I'm guessing they dont exist yet? Or have I missed it?

As long as you're using a Bashed Patch Deadly Dragons works fine and you'll even see those dragons. The only thing it doesn't do (I think?) is increase the base difficulty of the new dragons.

Even if you don't use a bashed patch, you just won't see those dragons randomly, which means you'll see similarly leveled, better looking, DD dragons instead. The reason no one has bothered specially updating any dragon difficulty mods to include them is because they're just higher leveled versions of vanilla dragons. Aside from naming consistency there's no real difference between higher level dragons already added by mods and the mod "take" on those dragons such as it will be.