The Double Edged Sword mastery is a bad mastery to take now
With the Double Edged Sword moved to Tier 4, I think it's pretty much the worst mastery to take in this tier. It's probably slightly better during early game but falls off during mid or late game when you compare the other two masteries in this tier, Bounty Hunter and Battle Trance. Once you kill at least 3 different champions, Bounty Hunter already outscales Double Edged Sword because you get a permanent 4.5% increased damage without taking any additional damage (which Double Edged Sword makes you take 2.5% additional damage all the time while dealing an additional 5% damage) and the max additional damage you can get with Bounty Hunter is 7.5% once you kill every 5 different champions. For champions that have high kill potential such as assassins and marksmen, I'd obviously take Bounty Hunter because I'd obviously already have killed 2 or 3 different champions by mid game if played right during early game and for champions who have lower kill potential such as tanks and supports, I'd take Battle Trance because I'd mostly assist the team as them so the early extra damage from Double Edged Sword is not needed for them either. I honestly don't think Double Edged Sword is comparable with the other two masteries in Tier 4 (especially Bounty Hunter).