At this point, it looks like that despite what the patch notes say, the two piece tier 9 bonus is still not critting like a physical attack. [edit: thanks Frost!] It does work with mortal shots, however. Update for sep 24th: They did something last night- everything is now working properly. Serpent sting is now critting like a physical attack and getting the benefit from all the crit magnifiers.
I forgot to mention when I wrote this, however, that kill shot is now back to sharing a minimum range with all other ranged attacks.
Also, the promised abyssal shatter never made it into the patch notes or trainers.