Killed this mob for months, and months,
Only ever had 2 walls pop, not 1 nor 3 or 4...2.
we fight him right in front of where he stands, 3 healers, 2 at the front near mages to rez...1 middle back to do that mage.
Only issue we ever have is you cannot be in the wall, or slightly off center. you need to be behind it, not touching it and dead center of it.
Make sure you have your settings turned up, if you run on bottom 2 choices the walls are only visable from about 10mtrs zoomed in close to your char, zoom out far...you wont ever see them.
on high quality i could have my camera zoomed out to max and see the 2 walls pop in any of the 6 locs for them (4 front) (2 back)