Example 1; Enemy player moves close to something small like a bush, and all 8 swarmer missiles hit the bush, enemy player is left unharmed, so is the bush. I wasted 8 missiles.
Example 2; Player aims and shoots over a short railing, all 8 swarmer missiles hit the 2 foot high railing. I wasted 8 missiles
In fact, the only instances where a swarmer is worth using is up close, and in large open areas. Everything else is a bit of a gamble really as these missiles seem to hit what they want to hit.
I wish I had the option to use something else in its place.