Is it typical for the metal of corner bead to be exposed after it is finished being mudded?
Examine any corner in any building and you'll find that the paint is on plaster, not metal.  (Interior paint - even with primer - will scrape off of metal way too easily)

The plaster is supposed to just cover the metal corner, neatly.

In short - your drywallers (if these are the same guys who botched all the screws) suck.