Alright, here it is. Instead of changing broader spell mechanics, which I think work fine for most spells, I simply change the mechanics of the two main combat series, which is where most of the problem with spells lies. Above all, I try to make sure that all of my experimental house-rules feel right thematically and can be integrated without blatant contradiction with text on cards, etc. I feel these meet both requirements. I have no doubt many of you will think it's too much of a buff, and I'll just simply say that I think you've gotten use to some spells being gimpier than they should be =P.

Wither, Shriveling, Dread Curse - These spells now operate as a "debuff" that lasts for a turn instead of having to be maintained. They only take hands on the round they are cast, and your hands are then freed if the combat goes subsequent rounds (regardless if the spell succeeds or fails). If you are still defeated by the enemy, another player can get the same bonus if they attack them the same turn. It makes them a good deal more powerful, as in my opinion they should be, and makes them compete less with magical weapons. Note that magical resistance/immunity apply as normal, and will grant half/no bonus to all attacks while they are active. +12 will also be the maximum bonus you can get against a weakened enemy.

Fist of Yog-Sothoth, Spectral Razor - These now work as "magical weapons" (although they are still considered spells and not weapons). They can be cast prior to engaging enemies (either during upkeep or movement phase). If cast successfully, they function for the remainder of your turn as weapons would. Note that even with this change, these 2 spells are still somewhat situational and will rarely shine, but it helps differentiate them from the above three.

That's it!

Also, see my stamina house-rule (one of the biggest issues in the game is how sanity and stamina aren't exactly balanced well):

During the movement phase, you can spend stamina to gain:
- Movement points on a one-for-one basis
- +2 to a single combat check (announced before the check is made)