Defensive towers( Cannons, Laser, Tesla, Snipes) should not be grouped together. This is known as a BDB(Big Dumb Bunch). They are strongly discouraged because they are very vulnerable to the catapult. Someone could easily 2 million pebble bomb or 5 million twig the group, and knock them all out, leaving the base defenseless, not counting booby traps.

(Just decided to revise your page, Proman.)