^I would imagine it happens a lot in 2 skill regions, with differing results.
1. At very low levels, some people don't respect the strength of cursing, and the player with the curser wins easily.
2. At some medium-high level, people are aware of these rankings, and one player buys Sea Hag because it's #1, while the other player thinks about the actual strategy and realizes you can just trash the curses, so it's not worth opening a negative-tempo card. In this case, the Sea Hag loses.
Now you will see good players say Sea Hag is "terrible" because they only play in situation 2 when they play down to someone who thinks Sea Hag is the best $4 card, and in mirrors. So in all the non-mirrors, Sea Hag is bad. And there's a lot of them since it's overrated.
But really Sea Hag is not that bad *overall*. You still actually have to buy it well over half the time, to avoid ending up in situation (1), which is worth something.
My statement 2 posts ago isn't quite correct. I meant that you should *also* consider non-mirror situations, not that you should consider them exclusively, as that has the same kind of pitfalls as only looking at mirrors.