I am not trying to say that it isn't situational, just that you said above:
and I can think of several situations where you would want to use it.
However, even without those situations, I don’t think it is so bad. You can’t move bad cards from the top of the deck like other cards, but it can still be very useful if you want to stack the villain deck. Assuming you are not playing against a villain that loves the trash (in those cases you would need to consider other things), look at what the power does for you you:
1) If you draw a really bad card, you then you know that the really bad cad (or at least one copy) is not on or near the top of the deck (and is now no longer in the the deck at all). This knowledge can be very useful.
2) If you get a no-so-bad card, put it on top, and you don’t have to worry about a bad card next turn, and you know the bad card is not on the bottomw of the deck.
Honestly, either option is good to know, if stacking the deck is something you want, and if you use it constantly, you will be in good shape. Is it as good as some of the other villain deck stacking stuff, no, if only because it only reveals a single card instead of 2 or 3. In other cases, you get to choose what would be the better card for the heroes. With Writhe, you have to go into saying “I am only try to avoid XYZ”. If XYZ doesn’t come up, move the card so it doesn’t come up. If it does, trash it. It is a slightly different way to look at things, but it can be extremely effective.
It does have some negatives, like trashing the card (which can sometimes be good), but it also has some positives like how it combos with other cards. But the Sentinels have other options, so being weaker/different isn’t so bad. However, as you pointing out up above, sometimes, even many times, straight damage, etc., is better. Straight damage/damage reduction, etc. being better, might be more of a reflection of those abilities being better than stacking the deck, especially with the Sentinels, than the ability being weaker.