Elixir of Wrath not working

I was testing Elixir of Wrath on Malzahar, and found out it doesn't work on his auto attacks(which deal physical damage). I further tested that it does not proc off his voidlings either(which are also physical damage and fall under a physical spell category as they apply blackcleaver stacks which "Dealing physical damage to an enemy champion" is in the tool tip, same as Wrath).

Anyone else have problems with typical AD champs(Rene/Riven/etc.)?