I've spent a fair amount of time poking at the code of this game. Here's some stuff I've figured out that might be helpful for anyone trying to beat the game normally.
Witch Trial
H attacks are weird. In stage 1, they never miss. Ever. Also they'll rarely increase pleasure by more than one, but that doesn't matter too much. This is actually sort of exploitable, you can switch to taking attacks yourself and play whatever five cards you want, and using H attacks whenever they're up will let you survive forever. You can build up your cost to the max of 20 this way, and even take pleasure all the way up to 60 if you want. (Though unless you're trying to beat this mode by making Lise orgasm, that probably isn't worth it, and it's pretty boring.)
In stage 2, they have a flat 50% chance to miss. 60 is still the max in stage 2.
In stage 3, there's a weird equation that if I'm reading it right, says that the first two H attacks in a turn will always miss, the third will have a 20% chance of missing, and any further ones will always hit.
I do not understand the logic here.
Anyway, bind or being in the middle of casting the damage-all spell will make them autohit again, like the tutorial popups tell you. There's another spell that can come up in stage 3 that reduces pleasure though, and this doesn't seem to, because of the way timing works - it only takes one turn, so the spell will have finished casting before you can deliberately take advantage of it.
Given the way damage escalates in later stages I find cheaper cards to be more useful in this mode, because if they'll only do one damage and get one-shot anyway, then being cheaper to get more out is more useful. But the Succubus card is incredibly useful, just because it can do everything - high attack and h-attack when you've got an opening, high hp and the defense ability to tank, bind to help keep the player's hp up.
Witch Hunt
This mode is pretty much all about not running out of cost, which is restored by varying amounts after an orgasm.
-For every two attacks that match the current weak point, 1 cost will be restored.
-The status effect from the "phantom stone" card will give an extra 6 cost per turn.
-The status effect from the "climax magical emission" card gives an extra 4 cost per turn. Oddly, this is harder to make than the "phantom stone" card, which gives more.
-Different levels of the "masochism" status effect give 3-5 cost.
-For the first five orgasms, you receive an extra 8 cost for 'draining mana'. Afterwards, it gives 1 per turn. (In theory, the function involved could return 0, but I don't see how that could actually happen given the way the whole thing works.
-Squirting (caused when more than 55 pleasure has been given during a turn with an an orgasm) gives an extra four cost. (The game lies to you on this. It displays 8, but that number is divided in half before being added to the cost.)
Now, I could go into detail about the resistance mechanics or how masochism works or some other things... but the thing is, once you make and use the two cards that give extra cost per turn (which don't need to be unlocked), then the cards that boost pleasure from attacks, you can with only a little care have constantly increasing cost, and keep playing the game pretty much forever doing whatever you want.
If you were going to try forgoing some or all of that for the challenge, I will say I think higher cost cards are more useful in this mode, since both hp and pleasure generally increase roughly linearly with cost. (And tentacle clothes are just absurdly powerful... but then, you've got to get 2000 score to get access to those, so you'd have to already beat everything without them to have them. So they only matter if you're replaying for fun or if someone adds an extra difficult mode.)
