QHull (and perhaps other good implementations of QuickHull) works really well and fast in many cases. However, we know theoretically that its worst case can be O(n^2). In practice I have not seen any numerical example with many dimensions (i.e., 20 or 100) where QHull works poorly.
Do you know of a numerical example where QHull works poorly, or gives the wrong result, or whatever that shows it cannot be applied here.
For multidimensional cases you have to generalize what A. Donda said: Generate a set of Points P with norm(p)==1 for each Point p in P. The convex hull is P (unless two points are identical) and will result in a bad running time of ~O(n^2)
For the 2D Case this will choose points on a circle, for 3D points on a sphere.