No matter what the AI leads the zombies to do, people will find a way to exploit them.
I'll never accept that statement as a valid attitude toward any game. It's repeated in this forum constantly as if it is fact, and it is not.
The AI should be understood and countered by the player as intended by the design of the game without exploits. Anything less is failure.
Try to find any developer of any respectable game make that statement. If this is the attitude with stupid zombies, this game is in for a world of hurt when the bandits come in.
I agree with random attacks on defense.
I agree with zombies attack weakest spot.
I agree with zombies take open route.
I think it should work like this though:
1) Zombies always start attacking at random points.
2) Zombies do not target weak spots until a weak spot is discovered.
3) Zombies do not take open paths to the player until an open path to the player is discovered.
4) Only zombies that are near (can see) another zombie that discovered a weak spot or an open path will join in. Otherwise, they continue their randomness until they discover or "see" another zombie discover.
Whatever happened to the meat bomb, or whatever they were calling it? It would be nice to have something in the game to manipulate AI within the intentional bounds of the game. Some real strategy to the tower defense portion of the game would be nice in general. If more focus was put on that, there would be less people looking for trashy exploits for starters. How about a few zombies that will target traps if they are damaged by them? Could be bad for traps, but at the same time, it could be a useful strategy to manipulate that behavior in your favor.