dubia cockroach

I just obtained about 30 dubia cockroaches. Once I have a sustainable colony would they be a good feeder for my Emp? And possibly my AZ bark if small enough?

yes...they will be a perfect feeder for your scorps...
plus they dont stink at all when compared to raising crickets =)

I am waiting for an order of 125 Dubia myself. I posted some questions on breeding some feeders and was pointed in the direction of the Dubia. The reason why I'm going that route myself is from what I've read is that they are actually a very healthy choice and would be great for any scorp. The exoskelton is supposed to be softer than other speicies and they are also supposed to be meater and easy to bread. When you bread them you would probably want to hang on to the adults for more breeding but you have any size of roach to feed your scorps. Large sub adults or whatever for your emp and maybe nymphs for the Bark Scorp. I'm a noob in the hobby but I've been doing a lot of reading on this lately.

I also have an order in transit now of 4 H. Spinifers and 3 H. Spinigerus on top of the Dubia's. And this is what I intend on feeding my scorps which are pretty similiar to yours I'd imagine.

I ordered my Dubias from TheRoachGuy.com and the site also has a great nutritional chart here: theroachguy.com/nutrition

So Ive had them a little while now and I count a more than what I had when I recieved them but I have one question that I cant find an answer to online. Do they molt? I only ask because Ive found about 4 that I cant tell whether its molted skin or if its a dead roach.

Check this out and scroll down to the humidity section. Quick answer: Yes they molt.
http://www.blapticadubiaroaches.com/ian-the-roach-ranch-care.html