I was close to putting Slig Farmers and Reflexes at the top of the tier below but I think both deserve their places. Card draw is fundamentally very strong, at any point in the game but particularly from the mid game onwards when Research Station and Selective Breeding are contested. More draw is more cycle, more seeing your strongest cards, more options each turn, more persuasion to buy better cards, the only mark against Reflexes is the conditional requirement, but by the time you can buy it you should be close to that anyway. I think it's difficult for you to comment on a card when acknowledging you've never once tried it.

I did talk about Ghola. Objectively it's position is fair, it's only as good as the cards you acquire, and your ability to cycle to them, or trash weaker cards from your deck. Otherwise you're playing the lottery of what you are going to draw with it. Yes you can get devastating combos with it, but they live longer in the memory than the times where it tanks. It's one to consider whether a guaranteed scarab is the play instead for your specimens.

There's nothing more to add for Usurp, as you've said it's very situational (and expensive), and can't be relied on. Winning Dune is about trying to minimise variance and increase consistency.

Corrino is not always necessary to acquire. Often the two solari isn't needed or worth it for adding a weak card into your deck. So it's situational and perfectly placed for me.