Armory only sets up an RPC connection to Core when running the auto bitcoind management. I'd prefer a solution that covers ever case.
I believe that 0.12 also includes some code that generates a temporary random RPC password if none is configured - and writes it to a file - to make it easier for local clients to use the RPC interface without requiring prior configuration.
EDIT: Don't know if this functionality is enabled in GUI mode, though, or only for bitcoind.
P.S. Out of curiosity, what does Armory currently use the RPC connection for? Just wondering what I'm missing out on, given I don't have Armory managing my Core instance.