I haven't been able to determine the exact trigger for this, but it repeatedly happened to me when I was trying to pull Salrand in Borean Tundra for a quest (she wouldn't pull, kept saying out of LoS and using DnD/Blood Boil directly on her wouldn't pull either), and it happened twice so far when I was farming Netherweave in Shadowmoon Valley. Here's a clip:

https://www.youtube.com/watch?v=U5CBza54e_8

It's probably happened to me a total of 8 times ever.

[Edit] I see in this one it says my placement wasn't in LoS. Maybe that's it, but it shouldn't cast then, right? In the example above with Salrand, there isn't anything visible that would put her out of LoS.

This is a weird one.
I tried reproducing this issue multiple times in different areas, but for me it worked perfectly.
Also I went to Salarand in Borean and I could pull her with Death and Decay.

So I'm guessing it's a local issue that happens with your game client.
Please delete the game Cache folder and see if it happens again.

Hi Tango,

I deleted the cache folder and tried to reproduce for a minute and I wasn't able to make it happen this time around. I'll keep trying, just in case.

Thank you!