I don't think the spike would need hard edges... It's shading looks decent from what I'm seeing there. Anywhere you have those sharp angles though, they should be separated into different groups. (I don't mean sharp as in the spike's point sharp, I mean sharp like perpendicular lines)
It's kind of hard to see, but it definitely looks like you didn't set up your smoothing groups properly. Remember that any 90 degree or sharp corners should be hard edges. If you do this and still get some shading issues, screw around with the smoothing groups to get a workable result. Any harsh shading issues on your low…