How far away from each other your towers are, matters. If you put 3 towers together, all 3 fall. And even when you put a space between each tower, they still take out 2 at a time.
At my speed, the best strategy is to have 2 towers, then a space. The attacker is going to destroy 2 towers anyway, so eliminating one of the spaces has no real consequence.
In a straight path, I’ve found that the most efficient order to have is:
Skull, space, Bomb Tower, Barricade + Firebolt.
This way, the Bomb Tower recieves last of the SB, leaving it with a ton of health. The Barricade gets the very end, and is hardly damaged. The Firebolt, then, cannot be hit through the barricade which has immediately stopped the hero.
However, bases don’t have quite that much space. So, to the experienced players, what are your clustering strategies?