I actually believe the Superworm makes a decent staple feeder.
The reason is that they will eat just about anything and are, therefore, extremely gut-loadable.
There are periods where my very finicky veiled (you know him as Kitty) will eat nothing else.
I have stopped worrying about this, and started super gut-loading the superworms.
I agree that zophobas kept in cereal or bran (whatever) and nothing else, are probably not the best staple food....but mine eat a variety of fruits and vegetables, cricketfood, and Total brand cereal.
Variety is the key to success, as is making sure every feeder you offer is as nutritious as it can possibly be.
-Brad