Any difference in elevation will negate ground strike right now. No joke, find somewhere where there's a street curb, wood planks laid out on the ground, the grass on Greenwich vs. the pathways, try and ground strike someone on the other side of it and you do no damage. Slopes on the main avenues, too, trying to hit a target that is up the slope from you will miss.
Also gonna add that for what seems to be similar reasons, Death Slam just fails to pull targets when they happen to be near a lot of these new features on the map. They are targeted, grabbed, then the hero catches on the "obstacle" they were standing on or near, and remain in place.