Since the strength of Rebuild (and to a lesser degree, other DA cards) only became "common knowledge" in late 2013
I don't think that's very relevant. The thing about good players (who should be overrepresented in the top 100) is that they realise that whatever manages to pass for "common knowledge" always lies somewhere between a disfigured caricature of the truth and misleading nonsense, so they just opt to use their own brain instead.
It took me personally about one game to figure out that Rebuild was powerful, and I left iso as a level 33, which is fairly mediocre. These are my Rebuild gainrates over different periods (I started out on Goko with Base+DA only, and gradually added the other expansions during the next two months):
03/15/2013 - 06/30/2013: 67 out of 76 pro games, or 88.2% of the time.
07/01/2013 - 12/31/2013: 108 out of 129 pro games, or 83.7% of the time.
01/01/2014 - 01/29/2015: 42 out of 57 pro games, or 73.3% of the time.
Before looking at my own data I thought that 74.4% was too low as well, but my own play convinces me enough to not have a strong opinion on the matter, and if a Dominion Oracle emerged who could resolve such issues and someone offered me to place a lot of money on "80% is closer to correct than 75%", I would politely decline.
The larger point, though, is that ~75% is still an insane amount for what is basically a single card strategy, to the point that there's little qualitative difference between "this card makes other cards irrelevant on 85% of boards" vs. "it does so only on 75% of them". If you look at the top 10 of this list--all cards gained more frequently than Rebuild--you'll see that none of these dictate a particular strategy on their own, not even Governor. In fact, many of them
open up strategic possibilities, they are expansive rather than constrictive; whereas in the vast majority of Rebuild games the path is paved and your sole job consists in not diverting too much from the racing line.