DBZ if Android 17 didnt protect himself with that orb, do you think piccolos smart attack woud of killed 17?

Yup... that attack could have destroyed Manhattan, if Piccolo had added a wider range to that attack... I mean, if Piccolo is stronger than a Super Saiyan, and Frieza could destroy a planet when he was weaker than a Super Saiyan (in his 4th form) than obviously 17 would have been blown to smithereens.