How to get Mistward Helm Casing?

I completed the Tangled Depths meta event twice (which means all four chak gerents were slain) but still did not get the Mistward Helm Casing.So, does that mean all four chak gerents have to be slain during the first time they came out? If so, can anyone provide some advice?Personally I feel three minutes are way to short to take one gerent down.
Thank you,

You just need to succeed at the Meta Event, which it sounds like you did twice alongside everyone else on the map at that time. I also completed the meta twice and didn't get the Helm Casing. On the second round, I took screenshots of the event completion pop-up windows as proof of completion and the Mistward Helm achievement track to show that it was still lacking the Helm Casing. I submitted these to Support in a Ticket to have them send me the Helm Casing.

At the time that I had submitted (several months ago), the issue was isolated. The Support Team was rigorous and thorough in vetting my request before sending the Helm Casing, so please expect a few responses with questions. Having the screenshots along with information on your server, play time, etc. will certainly be helpful.

So, in closing, give it a whirl a third time, but be prepared to document and take screenshots if the Helm Casing doesn't show up. Perhaps with a second documented case, they'll have a closer look to see if there's a root cause that can be found and fixed.