With how polymorph works with invested points, there is no reason to put any of your leveling points anywhere else but this skill once you invest the initial one point in the other lines of your choice.
Will this be revised?
Many spellbooks have higher requirements than 1 point in skills. Some skills have hidden benefits at higher levels, especially Summoning which gets bumps at 10 and 20 points.
But most importantly? Aesthetics. I won't be using Polymorph because I don't like the way it looks.
