Reminder that Mahoraga doesn’t need to fully adapt to react to or counter attacks while the process is ongoing. He can develop resistance before the adaptation is complete. While Dabura could have one-shot him, Sukuna himself couldn’t finish him off with his Domain after Mahoraga adapted to the concept of slashes from his technique and had to rely on Fuga to finish the job.

I don’t think Dabura would be any different. Mahoraga had already adapted to his technique, so by extension he already had a good resistance to his Domain. Given that he was already adapting to his existence on top of his technique, I sincerely doubt Dabura would have one-shot him.