I don't think people should look at things in terms of a single ship, though. It's a combination of that specific ship's power AND the empowerment it gives to the other vessels in the fleet.
The Marauder's power is pretty weak compared to some other level 6 powers, but it's absolutely huge when it's given in the context of supplementing an entire fleet's mobility at remote points. Coupling it with a planet with three frigate factories that is well behind the lines can bring sieges in behind you as you progress through enemy territories, summon flaks if you run into hangars, and generally react much quicker than any other race.
And since the ability only works for a limited time it can't even be used to rally reinforcements for your fleet from that 5 factory desert planet to your enemies base.
Not sure this is true. Timing it correctly once you've built a mass of frigates should deliver reinforcements in a cluster.