Canon 24-70 Mk II variation (by Lensrentals.com)

[Phenix205]

Roger has done a nice analysis.

http://www.lensrentals.com/blog/2012/11/canon-24-70-mk-ii-variation

Don't be surprised if your copy is not sharper than your beloved 70-200 II.

[weekendshooter]

you beat me to posting this!

One of the commenters' points about how you might be sorely disappointed if you already have a very good copy of the 24-70 I is quite disheartening; one would think Canon would have stricter standards for this lens considering its lengthy development time and exorbitant price.

[Dylan777]

Well...call me lucky if you want to, but I received my 24-70 II from the 1st patch. The lens is sharp, but it has little vignetting at 24mm.

 I decided to exchange for another copy. My replacement arrived Oct 31th, both sharpness and vignetting are about the same. Decided to keep the newer copy, couldn't help it

[amazin]

Does AFMA can help change this?

What is Canon after-sales policy toward this random quality "issue"?

[bdunbar79]

I tested mine out several times and it appears to be razor sharp.

[Mt Spokane Photography]

Does AFMA can help change this?

What is Canon after-sales policy toward this random quality "issue"?

No, AFMA is not a factor.
If a lens is out of Spec, Canon will fix it. 
All but three of the 70 were fine.  Variation is normal and to be expected.  Canon is not going to guarantee that you get the best of the best.  Even the lowest performing lenses were better than the best performing MK I lenses.