Firstly, my understanding about the percentage thingy is the same as how ColorlessGreen did - percentage of max HP removed from current HP.
I admit that my concern about the math was a bit flawed earlier. My main concern is the interaction between SoVs and SoDs. To be specific, using the usual Poisondial deck against any SoV decks. I have no doubt there'll be somebody helpful enough to share charts, SoSac calculator etc. but I still feel it's a hassle to use that. The only thing that I can think of right now is to tweak the percentage to something easier to calculate - 20%|30% for one turn perhaps?
Or, maybe I just need to sharpen my math and stop being lazy... 
Personally I find doing that sort of percentage math to be no more problematic than calculating bolt damage. All you'd need for a "SoSac calculator" is to open up the calculator on your computer and multiply your maxhp by either 0.4 or 0.48 if you're up against SoV or you're using SS. A chart showing the common numbers (i.e. the max hp you'd be at after using a given number of SoDs) would be posted basically instantly.
Poll
