Oh, I remember this...
You had a MASSIVE bad sightline on the bottom area, usually also having a point down in a put leads to spamming.
I fixed that in a4, and I have yet to see major spam problems for B, though I will think of something to try and counter this.
I want suggestions on how to artpass this, I was thinking spytech for around point B and the bottom area, but I have yet to decide on a area for A and the upper levels. I'd like to stay away from egyptian and medieval. That leaves me with farmland, desert, alpine/snow, swamp, and industrial/construction.