I believe you may have to import each address one-by-one into Armory. Not sure if you can import an entire wallet file or not. You can however, use functions within the console of QT to dump all the private keys ( Help > Debug window > Console > dumpprivkey your_wallet_address) which can be used to import them into Armory. You may have to unencrypt the wallet via the console first ( walletpassphrase <passphrase> <timeout> ). The timeout is how long the wallet decryption key is stored in memory.
Guide for offline transactions:
https://www.armoryguide.com/OfflineTransactions.htmlHope this helps!