Even though my power level is 251, the defense on this piece of armor was only 10. It had good stats, but I don't understand why the defense is so low.
The Destiny wiki classifies Omega Mechanos as Season 2 Eververse armor set; Season 1 being the Optimacy armor set. When searching for these pieces of gear on DestinyTracker, Optimacy and Omega Mechanos, they are shown with a 10 defense when acquired.
According to users on reddit, here and here, Eververse armor sets are design to always be dropped at 10 defense regardless of your current defense level or how you obtain it. This is speculated to prevent a pay-to-win status, since Bright/Illuminated Engrams can be purchased with real currency