Necro Feign death not working all the time, whats up?

[Topgunben]

about 10 mins ago i was running from Lguk to Innothule and i picked up about 12 trash mobs on my run. I cast FD, but i didnt lose aggro. so i did it again, and still no loss of aggro. 2 more times trying after that and i finally died. i am level 51, so most of these guys were only hitting me for about 10 to 30 hp, but they wore me down.

Anyway, this has happened to me before a couple times where no matter how many times i cast feign death, i cant shake the aggro. Specifically one time in LoIO in the sarnak fortress throne room. there are a ton of trash mobs in there, and i just wasnt able to drop aggro after casting FD 3 times.

hopefully someone can shed some light on what i am doing wrong.