I found that if you had invented the railgun weapon before entering this scenario, you actually had a weapon decent enough to provide an incredible amount of cover to nearby ships, on the assumption that your cannons were not reloading.
The problem there becomes that you are virtually required to have this one type of weapon (an instant-hit anti-light weapon, mostly. I think railclusters fill a similar role? I hesitate to put flak here, despite this possibly being their 'best' case) and If you didn't have it, it was indeed a race against the clock as it were.
Also, as this scales up (i did it a few times on a single hero, and once in a game with three), it gets weirder - If all 3 members work together and have good anti-base weapons, it can be incredibly easy(maybe one of them mounting anti-colonyship weapons). Without the cooperation, it became really difficult to operate properly against the increased strength of colonyships.
With all of that said - I really dont think this mission needed a nerf. I honestly dont. If anything, the ravenous shadow one needed looking at, for reasons of speed alone.