I discovered this yesterday when I was dueling a rogue. Apparently the way they changed blood boil is you cannot use the spell unless there is enemy within 10 yards, regardless if they're stealth or not. It also works with druid
I will clarify what exactly is blood boil (3.1 version)
You can now use it any time even if the targets don't have disease. But you can only use it if there is enemy within 10 yards of you. So you can spam blood boil without triggering blood runes unless rogues go near you trying to sap/cheapshot
So when fighting against rogues, you can just spam blood boil, and it is impossible for them to sap or start any opener on you. I tried this on a rogue who sprint with imp stealth tries to sap/cheapshot me, and I was able to get him out of stealth 100% of the time.
enjoy