Devourer and Vi

For the love of god stop buying this item on her. Her W is not her main source of damage. It is used for it's utility to shred tanks for your carries. Vi is a bruiser (fighter) and tank. She is there to dive the back-line and be disruptive. The best way for her to do this is buy getting AD, HP, and other tank stats with a bit of CDR to allow her to spam her Ult Q combo.

Please explain the thought process behind Devourer because Vi is in no way, shape, or form a consistent damage dealer.