Bahlak, the Sky Seer Bug?

I've encountered Bahlak, the Sky Seer in the T15 map about 3-4 times. Each time, after the boss summons a tornado, the tornado remains constant, and the boss stays inside. As a melee player, I can't deal damage because of the tornado, and I often die in one hit from some unknown attack. Even with 2800 health, 90000 armor, and max elemental resistance, it doesn't help at all.