Well, a rough night for us, but we learned some things.
I checked out logs, and it is the Arcane Shock that is killing us. Each time the Arcmage casts Arcane Shock(AS) the next AS causes 25% more damage, and that can stack up to 99 times. So, when we were trying to burn at the end and the Arcmage was free casting, on about his 5-6 cast he is one hitting someone. We will have to approach the 10% add wave different and just burn the adds down like normal. Interrupts are going to be very important, so get your interrupts out on your bars.
Backstab is our only other issue. After looking into it, the Assassins seem to only target the ranged dps. None of the healers got hit until a dps was already killed by an assassin. We have people that are getting killed by Backstab so we will have to be careful about turning our backs to them. Defensive CD's will need to be used before dying to them, it looks like the damage is between 100-200k if you don't get backstabbed or crit'ed, so their should be time to CD it. The good news is all of our ranged dps have a 90-100% damage reduction, so you can live through at least one assassin getting to you.
The other issue is our tank swaps. We have them down for the most part now, it got easier and easier as we pulled more. Tanking closer to the add spawn point made it much easier. I need to get better at timing my death strikes, I am taking to much damage right now.
Anyway, hope no one is to down. We were bound to hit a wall sooner or later, we will push through this guy next week and put tonight behind us!!! lol
Cya all tomorrow.