[LGM]

I just started playing gold, so I cannot comment about whether they are overpowered or not there. In 1.49, they are good for defending against a small fleet picking off planets. Deployed minefields count against your In Space unit limit and are limited in how many you can put in a square, so Weapon Platforms are certainly useful. I would suggest Null Space or Napalm to attack weapon platforms. The former will skip phased shields and take out platforms quicker. Also, since weapon platforms are static, you can make your secondary movement strategy to be Do not get Hurt so they will withdraw after firing.

If a player is spending all his resources to fill up every huge world with WPs, than he is not building offensve weapons (Fighters and Drones). It may be costly to take out the WP worlds, but you can blockade theminstead. Once you take out orbital shipyard bases, he can only build at most one ship there, so you can keep a Huge world blockaded quite cheaply with a small fleet. At least a huge reserve of fighters could overwhelm the blockading fleet.