To be fair, he didn't finish his training and doesn't have all his powers. So without the fist active he's just a dude who knows kung fu, Daredevil is a guy who knows martial arts and has super human reflexes thats why Daredevil would win against a untrained iron fist not using his chi.
I think the board room scene is a good indication of how many dudes Danny can take out without the chi, and how he can be dog piled if up against crazy numbers and not using the fist.
"You might be the dumbest Iron Fist ever" Yup.
Only people who can really damage Luke are those with super strength, Danny doesn't have that without the chi active. Gao has weird super strength/telekinesis blasts, Sowande has super strength as does Elektra from being the Black Sky.