If you are concerned that someone could access your blockchain.info wallet, then they can still access any bitcoins associated with that receiving address that you've imported into Armory.
Not if I delete the whole bitcoin.info account I presume?
I get the notion that you think different about bitcoins being safer in a local wallet? How so?
Depending on how you use each, a local wallet on an internet connected computer can be safer than blockchain.info, but the average user does not take any steps to ensure that it is.
Armory is a GREAT wallet. I'm not in any way implying that is is any less secure or safe than any other wallet. As a matter of fact, with the proper processes it can be the most secure and safe wallet available.
However, as long as you are choosing a wallet that provides you control over your private keys, safety and security will oftenl end up depending more on your processes and habits than which wallet you choose to use.
By importing a private key you are already choosing to forfeit a key safety feature that Armory provides (deterministic addresses).
Some questions to consider:
How often will you backup your wallet?
Where will you store the backups?
How many copies of the backups will you maintain?
Will you run any other software on the computer that is running Armory?
Are you using an air-gapped Armory offline wallet, or are you just using Armory on an online computer?
Are you encrypting your Armory wallet?
How secure is the password you've chosen for your Armory Wallet?
How likely are you to forget that password?
Is there a reason that you trust etothepi's C++/python programing more than you trust Piuk's javascript programming?
If you accidentally create a transaction with insufficient fee to be properly relayed and quickly mined, how will you handle the resulting situation?
Will you ever need/want to access your bitcoins when you are not sitting in front of your computer at home?
I'm sure there are other considerations as well. These are just the ones that quickly came to mind.