[Dragon of the void]

As far as I understand:

WP's are always "stacked", including their systems, no matter what. So you really have one planet, with several missile launchers, and several (redundant) multiplex tracking dev's.

The multiplex is trying to hit as many targets as possible with your missiles, meaning that only enough missiles to destroy the target are fired at one target (well, and I think the rest is just idle, as you describe).

The sollution would be to get rid of the multiplex, then you fire all missiles at once, at only one target. The next salvo 3 turns later picks another target, etc ...

Or use direct fire WP's. I think some combined WP's or Sat's that share the same component are pretty good (like "I prey for you", typo intended *g*)