WW6/IK4 is probably the weakest set for running GR's. Try using the Raekor 6/IK 4 Furious Charge build with Boulder Toss. The Might of the Earth 6/EQ build with Blade of the Tribes works well too. Personally I've gotten different builds for every class to do over 70 GR's, it takes some work & it doesn't hurt to pay a lot of attention to diablofans for ideas. Even if you just check diabloprogress to see which builds are at the top of the leaderboards, you will have better luck. In a perfect world, I wish that every set of gear & every build had the same potential but they do not.