exactly that why I reduced second skill dmg by 50% at all levels. Although that might be too much. I also had other skills reduce his second skill cooldown like ult while nerfing his ult a little so you could still be decent while entering fights but not to the point u oneshot everyone.
but u could cast skill 1 at the same time as skill 2. So i think dmg has to be nerfed completely. He is top banned and picked hero in mythical glory. In trade off, you could give him substainibility and mobility in exchange for insane dmg. So skill 1 has to be buffed more than skill 2 but dmg should still be less than current skill 2.