Wierdest game lag ive ever had

So last night, right before logging out. I was grinding on boars for a quest and a hunter asked me to help with 'Colossal Menace'. For those of you who havent done the quest it involves killing a bunch of Giants. So, I grouped up with the hunter and we headed to the Giant killing area. After killing the first Giant, the hunter dissapeared. Then I see a Giant get attacked but it immediatly dissapeared. I sent a message to the Hunter about what was happening, but I dont know if she saw the message. Eventually her pet shows up, but the hunter is still invisible. When I could see the pet I could see the Giant being attacked and I was getting quest completion. So, I kept at it. Final giant ended up killing the hunter (cause I couldnt see or target her) and then me. After I ran to my corpse the hunter is visible again.

I'm pretty sure the hunter wasnt a chinese gold farmer or a hacker because she asked me to group with her. But I figure it must have been something like that to cause such a bad technical flaw. Ive never experienced something like that from WOW in several years of play.