No current and up to date password and security system can be hacked. You ever wonder why we can no longer retrieve our passwords, but only reset them? It’s because the information you just sent through is secured using encryption keys and never actually stored anywhere.
So if someone was to hack in and find the password code they than need the key to decrypt it, and if you use the generator, it makes another key that is than sent to Blizzard and if the keys match, you get in. Those keys are changed every minute, so unless you can hack into their system, find the place the keys are stored, figure out how to decrypt the keys without the authenticator, you would need to find the key and decrypt it once a minute.
Possible, but highly unlikely someone is going to go through all that hassle just for one persons account.
Funny you say that, because here in Australia it probably cost less to buy the cheapest phone than it does to get an authenticator made.