So why not to use the weighted system?

You can easily make separate spam buttons, 1. for aoe spam (HB, NS/PS + FS) and 2. for obliterate spam (OB + FS).

Button 1. also puts diseases on target and both 1. and 2. also take care of the runic power dump.

NS is definitely better for pvp and PS maybe for pve (I dont know much about that).