My latest solution is having Magic-Resistant diseases, and making Cure Disease one-try. So, for example, the Grey Death, which is often fatal and has Magic Resistance 10, can be a real threat to a society. This seems to be the best one so far. I think it's also appropriate for some diseases, especially "true" leprosy, to be Cure Disease immune.
Why the Focus On Disease?
I think it's reasonable to ask why I worry about this. After all, no-one really wants to roleplay having cholera (roll 13 vs. HT 11: "OK, you poop yourself again and are Terribly Dehydrated.") For me, it's more a question of world-building than the actual gameplay. My gameworld is definitely late medieval Europe in inspiration, and even a cursory read of the time period should give you an idea of how constant and present the threat of disease was. Some, like leprosy, were a terror from the biblical age on. To have a universal panacea like Cure Disease really changes the tone away from what I'm looking for. Plus, while I don't want to constantly affect the PCs with nasty sicknesses, they should occasionally face an actual threat from it.