+11% is fine. In SNG play you'll experience times when you'll lose a ton of games in succession... it can be frustrating (even while playing optimally)... in sng's.. shyt happens.
So... to maintain an ROI of +11%, that's pretty good. Keep at 'er.
I'd guesstimate that some of the 'winning' players at $2 level might have an ROI of +15% (maybe some cases of +20%).