Giant Killer is working in game, but only a literal translation of the skill. If you inspect the target, there is a "size" attribute. Majority of the targets you see are "medium" sized. Minotaurs and Ogres are Large.
As many anticipated, picking a smaller race "should" trigger this, to provide advantages and builds for specialized playstyles, but this does not work in game.
A simple "if target size > attacker size = giant killer proc" but right now it simply parses for any target with large or bigger in the size tag.
