The curse status is awful, because first of all it instantly kills you.
So that sucks right off the bat, but then you spawn at your bonfire with 1/2 health. And yeah it stacks up to 1/8 health but no lower (that doesn't mean it still isn't a one hit kill).It only takes 3 hits of curse to get down to 1/8 health though, and I can't think of anything that will let you live in this game when you have 1/8 health.
The un-curse item costs 6k from the person close to the area where enemies have curse and 3k far away. If you go all the way to the person who sells it at 3k you'll have enough money to buy 2 of 3 un-curse items. I was hoping there would be a de-curse miracle but I don't think there is one. :/
Basically, don't even go near enemies with curse unless you have a bunch of de-curse items. Farm them, get as many as possible. When you run out get more. It is NOT worth the hassle to try and farm for 3k or 6k souls when you can't be hit at all.