No it is not. Tonight, put the phone on the charger and restart it. If there was an issue with Google+ this should clear it. If it is still high on the list, it will indeed need to be looked into. Google+ should NOT be at the top.
On the S3 the main battery users are the Screen and Cell Standby. Any decently intensive apps could make it up there if you use them a lot as well. It would take a fair bit to get over those 2 though. Example: Right now I'm sitting at 59% screen, 22% cell standby, 8% internet. Usage and settings can shuffle things around a fair bit, but you can pretty well and count on those 2 being the top 2 in most cases.
PS: In that battery window, you can also select individual processes to see their usage times, time without signal ( on the cell standby ), wakelocks, and a few other things. Then you can also click on the graph at the top for a better graph view. This second one is very important for watching for Wakelocks.
A wakelock is where an app asks the phone to stay awake even the screen is off. A normal example is Pandora. You want to keep streaming the music, but you want the screen off to save battery. So, while playing music, Pandora always keeps the phone awake. However, sometimes an app or service goes haywire and sends wakelocks non-stop killing your battery as the phone never goes to sleep.
You can compare the blue bars "Screen On" and "Awake". Those 2 should usually line up really closely. However, any time using for example Pandora while the screen is off will obviously cause discrepancies. Also, for anything such as email to sync, they have to very briefly wake the phone. So, small lines of awake while the screen is off is normal. For a wakelock problem, what you are looking for is a completely solid Awake bar, while you still had sizable stretches of the phone off and idle.
