User blog comment:The5lacker/Varus is not a normal AD carry/@comment-6906412-20130617034427

Alright, so Varus is an AD carry that plays similarly to a ranged AD caster more than anything. You often find Varus is the choice of ADC for people that like to play midlane casters, since they share similar styles. Despite the fact that Varus has %HP scaling with AP, hybrid characters are generally less effective than pure AD or AP carries due to the fact that their scalings are NOT high enough to support either stat when build hybrid. Although my friends and I have done pure AP Varus and Mage Fortune before (the only item not purely AP being Guinsoo's Rageblade), hybrid on either champion isnt as effective as pure AP which isnt as strong as traditional AD.

I do agree that the AP on-hit scalings with Nashor's and Spellblade are strong, but when you need high and consistent damage that ISNT reliant on spell hits (considering Varus' cooldowns are also relatively long, even with max CDR so you can't proc blight every 3 hits ANYWAY) AD carry is the best way to go. A few % more HP damage in blight from AP can easily be compensated for by substituting for another BT or even the Statikk Shiv passive.