Stop when you get the debuff. She doesn't spawn the mobs, she just gives you a debuff and when you hit her/cast any skill when you still have that debuff, the mobs will spawn. And yes, if your healer gets that debuff, stop healing until it disappears. That debuff stays for a few seconds, if you accidentally hit and a mob spawns, better kite it and wait until you're free from any debuff then kill it. I suggest you spread out a bit so not all members get the debuff at the same time. And yes, that includes tank and healer too.