So, there's a quest in Zul 'Drak called the fire's still hot. Here
Basically, the fire counts as a mob, and you have to spray the water on it 3 - 4 times to put it out. However, the water doesn't activate the GCD, so you can still fight while doing this.
Now the bug is that when you put out the fire, it counts as a mob, so if you're one of those classes that gets extra something after a kill, it is very useful.
I was doing this on my death knight, who gets 20 runic power and about 900 HP.
This is a fairly useful bug, because there are lots of fires in that village, as well as NPC's that drop lots of frostweave.
just pop a D&D, stand infront of a spot with atleast 2 fires, and
#1. let your D&D do damage
#2. Attack them yourself
#3. put out the fires
You can do this all at the same time by binding the water to a key you can easily press while in combat.
Just keep doing this and you can grind like crazy, recieving ~1k hp every 5 seconds.