Sounds to me like the low (L) limit screw is not adjusted properly. You said that at one point everything was working properly other than the chain was rubbing when you were in the large chainring and smallest cogs combination. Then you took it to the LBS. I suspect the mechanic meant to adjust the high (H) limit screw to allow the front derailleur to move further out slightly (to stop the rub). The may also have adjusted the low limit screw where the front derailleur does not move far enough inboard (toward the frame). You should not have cable slack when in the smallest chainring. I suggest that with the chain on the small chainring and the largest cog, turn the low limit screw counterclockwise until the inner art of the cage is not hitting the chain. After this test your shifting in all combinations. If you turn the low limit screw out to much, the only problem could be the chain over shifting and coming off the small chainring as you downshift. In this case, you need to screw the low limit screw in slightly.

Good luck.