When doing the export, make sure that you select "Include Unused (Address Pool)"... (I'd also recommend "omit spaces from key data" to make the copy/pasting of the private keys easier
)
Being Offline, Armory has no way to tell if your addresses/keys have been used or not... so they're ALL marked as unused and by default, when you do the export, it doesn't show you what it thinks are "unused" addresses/keys.
By selecting this option, Armory will output ALL the pre-generated addresses/keys in the wallet... regardless of whether or not it thinks they've actually been used