I was under the impression that skilll ratings given in LotR for NPCs are skill ranks, not ranks plus modifer. (So the Witch King would add in his bearing modifer to 15 skill ranks!).
I agree that he is certainly a cut above the normal character, but the same can be said for most of the powerful character in Middle Earth (especially for 1st age characters!).
I think the offical maximumun number of skill RANKSis 12, not 12+attribute mod. I was suggesting the latter to account for some of the write-up given in the book.