First, in my opinion, I think the AI adjustments to the skill (and reactions to other skills too, like shieldwall) are great and going in the right direction!
With regard to the Spearwall experience, I noticed the same as you that the AI tend to avoid spearwalls now, but not always, as Sky mentioned. In addition to having no choice on choke points, I also notice the AI may have a “skill confidence check” routine where it knows that I just put up a Spearwall with a level 1 recruit with bad melee skill, so actually it doesn’t mind charging at him and seeing his spear consequently whiff.
In short, with more I in AI, I think this is a good change. As awesome as it was for my team to have the AI impale themselves like mindless zombies on my spearwalls, it was just bad AI, so the new challenging behavior is so very welcome. The fact that the AI avoid it under certain conditions is exactly something that makes the skill even more useful now in a tactical way, as Sky pointed out (i.e. if the enemy wants to take the scenic route, around my spearwall, please feel free to take some arrows in the face while they are it) — the AI adapted to player tactics, now the players get to adapt to the AI tactics, and good gameplay ensues!
So, IMO I wouldn’t call it a nerf to Spearwall, but an upgrade to the AI.