You can't directly compare Davao with the rest of Mindanao. Davao has the rule of a very strict mayor. So in terms of general street crime is very safe.
In my opinion, safer than Manila and Makati.
As for the rest of Mindanao, I'd call you a fool to go into the Muslim seperatist region. Cagayan de Oreo (north) is not as safe (or developed) as Davao.
Of course developed areas (Malls, Airports, Trains) attract terrorists, but thats the same all over the world. You take your chances with everyone else.
