Why does this drop the 되?
되다 roughly means to become, in this case it means "to get fired" I think
So if you say you are fired you wouldn't use it
“되/해야” (must) is different from just 야, which is a verbal exclamation. Like instead of "You must be fired", it's just simply "you're fired!"
Is "해고이다" a reflexive causative form i.e. to get oneself fired?
Why does it sound very similar to "너 내거야"?