just played a game where i attacked a Salaman Daredevil 3 times and no deflect....naturally i assumed he didnt set it but then what do ya know the 4th attack it triggers. I did notice though the attacks it didnt trigger on were range attacks.....and the attack it did trigger on was melee. Not sure but could be something to do with it.
You can target a champion with deflect and the champ with deflect will only deflect the one you targeted