It was a little different for me than a description above.
Maybe it's due to the fact that I cleared every floor instead of climbing the wall. I told Gortash I'd think about the deal as well, but no dialogue with him was triggered during confrontation. He and two of his bodyguard took their turns while I fought with security below by the way, but they couldn't/wouldn't get down to me, they were just repeating same actions over and over. Once I got up to his floor he seemed to notice and left the hall to fight me on the walls.
Karlach reacted to his death with anger - she stated that all of her suffering was for nothing, and Gortash's death didn't change anything or help improve her situation.
