I do suspect they derail from the long straight paths as well, but noone has ever tried deploying from there so I can't say for sure. However, if they do derail, they would be more likely to go to the "closer" walls relatively to the paths, which are the outside ones. Townhall has no effects on WB's AI.
http://i49.tinypic.com/3516edg.jpg
Ah ok. Then, yes, you are correct. Someone pointed that out as well, earlier in this thread. Those are the 2 weakest points of this layout vs WB's AI. Noone has tried deploying WBs there yet though so I'm not sure if they would go straight (black) or get attracted to the strip (purple). However, I do think you are right about them going straight (black). I have thought about this and came up with a simple solution. I can attract WBs deployed from these precise spawn points away from the weak points by placing a single spike where the yellow dots are. I havn't done it yet just for the sake of a "clean" look. Plus, noone has tried to deploy WBs there yet, and I want to see if they do in fact go straight instead of get attracted to the zigzag :o Great analysis btw! Only people with sufficient knowledge of AI would be able to point out these precise weak spots.