How to get bitcoin P2SH (3*) address balance with bitcoind
The Core client will only update its balance when it registers transaction outputs that it is able to fully spend. So, if you don't have all of the multisig keys in your wallet, it won't keep track of the balance. What you're looking for is support for watch-only addresses, which should be coming soon (https://github.com/bitcoin/bitcoin/pull/4045/commits), but is definitely not available in 0.8.6.

In short, without writing some custom scripting, there is no way to do this with the current Core client.