You can find the official page on gratuities here. Gives the recommended tip along with the position.
I read in another thread that the concierge staff has been changed from being full-salary employees to gratuity-subsidized. The concierge aren't noted at all on Disney's tipping guideline chart, unless they're considering them your 'stateroom host'. Somehow I don't think that's the case.
What have people been tipping their concierge lately? I don't think I can really compare it to what I've tipped them at the resort since what they'll do for me will probably be quite different.