As you already mentioned, in the upcoming patch there is a change to Vial of Shadows that should reduce some of the burst damage you are experiencing in PvP.
Dying in openers certainly isn't fun, and can be incredibly frustrating if you're the one on the receiving end of such a coordinated attack, but don't give up! In addition to perhaps taking some time to focus on other activities such as Rated and unrated Battlegrounds where you have more people to watch your back, you might also consider browsing some PvP videos from other members of the community to not only help inspire you, but to also arm you with a further arsenal of tactics that you can use to your own advantage against opposing teams.
Also, from my own experience, when I was having a lot of trouble against a certain class or spec that I felt countered my usual tactics, I found it helpful to sometimes grab a friend that played that class and spent some time dueling them so that they could critique me on areas where I could improve my skills, including my timing on using certain abilities, and how I could counter some of their own tactics. That way when I stepped back into arenas, I was more confident in my own skills and felt better-prepared for how to expose the weaknesses of my enemies.
Keep at it, and remember there are players out there equally as scared to see you step out onto the Arena floor. :)
Ok, I watched some videos.
I could try an infinite number of possibilities and still be unable to counter/avoid this in any situation.
Lets be honest, you can't balance PvE and PvP at the same time while still having so many different class/spec combinations. At that rate, they can't even keep one of those balanced so how are we to expect them to balance both at the same time?
If you want balanced PvP, find another game because WoW will never have balance.