Never has a power sounded so extremely cool and been so very worthless. First, I have to conquer a planet without allies and without a power that aids me in the encounter, then my reward is that I don't have to leave ships on the planet to hold the colony? That's a huge challenge to accomplish for a comparatively insignificant reward. At this moment, unless there is some factor I am overlooking completely, it is by far the worst power in single-alien games. Surely everyone knows the ability to destroy a planet is insignificant next to the power of the Force.
There's a little more to it than that.
1. You've already noted that the power means that you don't have to keep even one ship on a foreign planet. This means that towards the end game, you could have 4 more ships available for use. Yes, that's a slight advantage.
2. Another advantage is that those devoured planets can't be taken away from you. Even if you lose your power, they still count.
3. The last advantage is the super flare which allows the Locust to possibly destroy a planet with other ships on it. When you get that, you have the potential to reduce other players' scores without harming your score.
Yes, the Locust starts off a little weak without its flare. However, being underestimated by other players is not all that bad. Plus, if you get the Locust Super Flare, suddenly, you're changing the flow of the game.
I loved the Star Wars quote.