You are right that there are a lot of nuances to the stats, so they need to be treated carefully. For example, there are cards that are normally bad but have niche use, or cards that have a high skill requirement but in the right hands can be interesting and add to the game (Growing Farm is a good example).
However, that doesn't mean the stats have no use at all. To take your example of Roughcaster (though to be clear, Roughcaster isn't banned!). The data set I linked to has 599 games where Roughcaster was dealt in 4-player games without additional action spaces. It was played in 48 games and played in a winning farm in 7 games. The equivalent numbers for 4-player AAS games are 183, 16, 2. In other words, it is rarely played, and even when it is played, it wins much less than 25% of the time in 4 player games.
That isn't conclusive. Maybe it's one of the fun/high skill requirement etc cards which the stats are hiding. But then a qualitative discussion helps. In my opinion, Roughcaster both boring and pushes you towards a strategy which is normally bad (multiple single build actions). Others can disagree with that - and people did, which is why Roughcaster did not end up on the list. But others, like Catcher, Breeder Buyer etc etc, are both extremely weak on the stats, and qualitatively boring and and unhelpful to almost all strategies. So they got included.
