The BM ranking list is meant as a starting point for conversation and further analysis. It is not meant to be an absolute rigid gospel. Valuable insights can still be gained from the data when comparing cards of similar type. Let me explain what I mean by using Marauder as an example.
Junking attacks are known to be quite strong in Dominion. They make engine building difficult and are shown to be very strong in BM simulation. Marauder is shown to be weak in BM simulation. So the question arises "Why are junking attacks like Sea Hag, Witch, and Mountebank so much better at BM than Marauder?" The answer to this question may also be important to engines (and in fact is) since it must be a specific property of Marauder.
An initial guess at this question would be "Perhaps it is because Marauder gives out ruins instead of curses". However, when we look at Cultist we see that it does well against BM. So what are the differences between Marauder and Cultist?
Marauder gains a Spoils while Cultist provides +2 cards and the ability to play another Cultist. This shows us that Marauder provides a delayed economy boost while Cultist provides a cycling boost and the ability to possibly attack/cycle again. Therefore, by looking at sample games we can conclude that Cultist will junk your opponents deck faster than Marauder and that this effect is stronger at defeating BM than gaining a Spoils. This is important for engine building as well. If you are building against Cultists you are going to be swarmed with junk faster than if playing against Marauder. Marauder also gains a Spoils which further delays the time until the next Marauder play.
However, then the question kind of goes backwards. "Sea Hag does not provide any cycling. Why does it outperform Marauder against BM?"
The two reasons are that Sea Hag junks immediately to the top of an opponents deck and that curses are always dead cards as well as -1 vp. The gaining of Spoils is not strong enough to compensate for these weaknesses in a BM match. This is important when building engines. Sea Hags attack often replaces a Copper with Curse during the early turns of the game. This can prevent key purchases of 5 cost cards or force the purchase of nothing/2 cost card. As we have learned from experience, the first few turns often have the biggest impact on the rest of the game. Marauder can't possibly have any impact on an opponent until Turn 5 at the earliest and often it is later. Even then, 2 of the 5 ruins (Abandoned Mine/Ruined Library) can be barely noticeable if they show up in a hand without other actions. Survivors can be helpful early on as well. As we have seen with Cultist, ruins are much more painful when they are given in large quantities causing them to behave more like Curses. We begin to see Marauder as a card that takes some time to cause damage to opponents and, more specifically, does little harm to opponents during the critical early turns of the game.
The next thing we need to look at more closely is Spoils. Simulation has shown us that gaining Spoils alone is not very powerful against BM. So what is the best use of Spoils? For the answer to this question I think about my experiences with another Spoils gainer, Bandit Camp. Bandit Camp is great for draw your deck engines because it allows the spending power of gold without being worried that that gold will get in the way of starting the engine up on your turn. Marauder can be used in much the same way. In an engine you are able to play Marauder frequently, making it damaging like Cultist while also generating some solid spending money. This is where Marauder becomes a true gem.
Based on this analysis I come to the conclusion that by opening with Marauder it is almost as if you have opened with a curse. Your deck is not yet ready to use Marauder to its full capacity and the gaining of Spoils is too slow to help you get there. Sea Hag's attack is powerful enough that it compensates for the early tempo loss. Marauder's is not.
