Diablo 2 Patch 1.13c

I could see fixing any potential wall climbing exploits in battlegrounds, or even around capital cities and PVP objectives, but they fixed it universally. It wasn't a hack or anything, people just tried to run up walls. There were "tricks" to it like walking backwards, or jumping at just the right spot that you might hit 1 in 100 tries. And it could hardly be exploiting for much other than entertainment value. The whole point was to find new areas, like Hyjal. I think that's one of the coolest things I've ever experienced in the game was when I was running through the empty Hyjal zone on my server and saw the World Tree and even a little sign that blizzard placed that said "caution! under construction" or something along those lines. The only way you could get there was by wall climbing and blinking through invisible walls. Naturally, they fixed it, so nobody can go there anymore to see how cool it is.

I haven't been in the Hyjal raid dungeon so I don't know how the two compare.