I got it after a bout a week. try on hijacked from the side alley ways you don't need to aim super high just high enough to cler the little room or hot tub. lots of people rush these ways so it will eventually hit. also check your game afterwards in theatre to see where your axes are landing. hope it helps.
Just got mine on slums in Domination. C flag to A flag at the start of the match. Put your back to the 2 barrels that are in front of you when you spawn aim just over the cross on top of the church. Got it on the first try with that method. I tried it over 10 times on raid domination because I read that was the easiest. I never could get to the spot quick enough on raid by the time it landed the other team had already capped the A or C flag and had moved on. On slums you can throw the tomahawk before they get to the A flag so the timing is better.