This arena has been a thorn in the side of my core group for a long time. It's not that we're not good enough to get through it, though we have never actually completed the final boss. The major barriers for us to complete this arena is time (we have 1 player from each timezone is the US) and more recently, horrible performance issues that continue to get worse as you progress through the arena.
I'm not sure what the cause for the degredation in game performance is, but it seems like the longer a single instance is open, the more the performance issues degrade. For instance, our most recent run STARTED with our tank being unable to taunt because the game said he did not have sword/shield equipped - when I could see that he clearly had one equipped. After logging out and logging in, this minor issue was addressed, but then two different players got kicked throughout the course of the first 9 rounds.
Then we had several wipes in round 5 because the players who had the shadow curse were standing on the plates, but either due to desync or some other glitch, the game simply did not detect them as being on the plates and they got insta-killed.
I'm well aware that this game will never be perfect and free of bugs. Ideally, these kinds of issues would be addressed so that we can have clean runs that are less time consuming and then we can continue to make progress in the arena, but I don't think that is a reality for Zos at this point. Outside of that, something else should be implemented that will allow groups to pick up at the same point they left off - something similar to the quest in Maelstrom. If all players are at a different level in VDSA, the game can simply make you start at the lowest level of completion. You can even make the quest re-set if you don't finish within a week (a-la Destiny). But something like this needs to be done as trying to get through the content right now is just an exercise of frustration because if it is not a time issue, its a game performance issue that is a barrier to completion. At least with a quest acting like a check point, you have the option of leaving, clearing cache and resetting the instance to hopefully resolve some of the performance issues.