Two casters, both in melee and at range are unable to complete this boss. The mechanics would not allow it. We both kept getting consumed at the same time resulting in a reset. Theoretically, we could have kept going at that rate until the cows came home.
The only solution was for me to get my tanking character. Even then it was cutting it close. As soon as my friend was pulled in, they had about two seconds to get out before I phased in. If they were too slow, the encounter reset. Not an ideal way to handle it. Especially since this is tier boss if you are farming for the appearance. I had to cut my loss this time and miss out on drop for my mage.