This has been in the game since day one, so why not continue to complain about it a year later.
Wall AI has NO LOGIC whatsoever on what it targets. It randomly ignores front line units and one shots catas, or trashes back line units while you fumble with the shit tier lag to recall the units with Elena. Or even better, it instantly kills Elena then drops a fat dick on your gold archers and a few catas because who doesnt like replacing 2k diamond catas.
This is by far the most obnoxious BUG in the game. It is impossible to consistently predict how wall ranged units will behave, other than that right side ninjas will ALWAYS target your right side cata. Why the hell hasnt this been fixed? Wall ranged should target the front line until it is dead.