User blog comment:Willbachbakal/(Champion Rework) Varus, the Arrow of Retribution/@comment-25228021-20150501160206/@comment-25228021-20150503183658

You would really have to detonate a bunch of Blight stacks to refresh Parting Shot for a second teamfight use. Without Runaan's it's pretty much impossible because you're going to have a hard time applying your stacks at all. CDR isn't a very good stat on Varus, even AP, and Nashor's Tooth is probably going to be his only CDR item if he has it. With the standard duration of teamfights Varus would be lucky to have a second shot at firing his Parting Shot. (yay for bad jokes)

Although it won't be much of a problem because apparently you want AP Varus to whittle down the tank, which he honestly will be good enough at, unless minions or the tank can just jump at him from AA range.