Riot specifically programmed Xin Zhao to be broken with Devourer, and surprise, he's broken.
Riot changed his q from an on-attack to an on-hit with the release of Devourer, just so he get off his q in two-hits. This has made him incredably strong, with his roughly halfing the time it takes for him to knock people up. He's now the second highest win rate jungler, perhaps highest win rate jungler, since Skarner just got hot fixed. He's also the third highest play rate, barely loosing to Skarner and Lee Sin. (Source)
Riot needs to do something about this solo-q monster, and reverting this change on his q would be an obvious fix.