According to a blue post by Daelo, the lead encounter designer, two bug fixes to Val'kyr Twins were just deployed to increase the difficulty of the encounter. The first fix makes it so Surge of Light and Surge of Darkness are cast properly on normal difficulties, and the second addresses the fact that Light Vortex was doing less damage than Dark Vortex.

In addition, the rate at which Concentrated Light and Concentrated Darkness spawns has increased.