Let me clarify (Ive been away from the forum for a while, so sorry for the late response)..
When I said Pak's are "easy" it's a relative term. For a level 8, who has solid foundations, and should know how to cast handstand, drop to kip, it is a fairly easy skill to do progressions for.
Yes, it can take as much as a year to learn. It can take 2 years! However, there are many drills that can be done safely, indepenently, with guidance, to develop the feel for the skill.
I think of a pak as more of a visual skill than a timing skill. Much like straddle backs, if you dont see where youre going, it's generally unsafe. (again, my opinion and how I coach)
As I see it, Nastia struggles with hers because she does all of her release moves so big. She, and her father, and the much of the audience, enjoy high flying, really exaggerated skills (look at her geinger!). Look at most other pak saltos and you will not see that hard jolt on the low bar catch like hers. She is falling early and struggling to kip because of the impact, not because it's a hard skill. In my opinion, the way she does it will lead to injury in her shoulders.
I look at most gymnastics skills and I have come up with a basic principle - gymnastics is based on natural motion of the body - therefore, gymnastics is natural and, quite frankly, "easy." It is the training of your body, mind, and the methods for doing the skills that takes time and effort and practice to perfect, which is "hard." There is a reason we encourage toe point on almost every skill in gymnastics, and it sure isnt because it looks pretty.
Just my 2 cents...
Ryan