Well, if this was real life, and I knew that my cannons could do fire damage to some nasty flying bats flying over my head, I would not hesitate to shoot.
However...we all know that artillery has it's flaws in KR... especially that "SHOOT HERE DAMN IT" problem, and I can only imagine that, if they were to shoot more enemies...more larger groups would pass free.
Also, if you think about it, you can pass most levels with artillery only...still, I agree, it's something your brain detects as WRONG.
MaGnUs wrote:...inspired by a screenshot someone posted, at the topmost row I built three artillery towers.
The picture Magnus refers to is probably
this.