The original equipment shackle problems are caused by using cheap imported steel that is 5mm thick instead of the 1/4" that the suspension was designed for. In addition, the holes are punched out rather than bored. This punching process causes a shear and break that has only about 40% of the hole available for engagement with the splines on the bolts. If the bolt is not completely retained, the movement will cause the wear seen in the OP's photo. Look how the steel is rolled towards the hole in the photo, this is no way to produce the shackle and expect it to last.
I made my own shackles from heat-treated alloy steel and bored the holes properly. I have no clue if the thicker HD shackles are made properly. If the holes were punched in an even thicker plate and the bolt splines were put in the bell-mouthed side, failure could happen just the same.
If the wet bolt kit used actual bronze bushings, rather than oilite, they probably wouldn't split and chip like mine did. Unless a grease channel is cut inside the bushing there is little chance of lubricating it on the loaded side. Cut a figure 8 inside with a Dremel tool before installing.