To give some idea of what a natural growth rate is (for a table acro, anyways),
here is a link to a National Geographic article that shows a reef in the Phoenix islands.
This reef suffered a bleaching event in 2002 and the author went back in 2009 to find a table acro that had grown 4 feet in the 7 years since the bleaching event.
How many of us have 7 year old acros that are 4 feet across?
Given enough room, there are probably a few tanks out there that the corals could come close, so I don't think we are all that far from being fully successful raising corals.
Gives you an idea what type of growth you could be aiming for, anyways.