Of course, if the ship is one kilometer long and the breach would envelop the ship in six hours, the breach should have been noticeably moving.
The Enterprise D is about 640 meters long, if I recall.
640 meters / 6 hours = 2.96 cm/second. Quite noticeable to the human eye.
As for the solution to Cause and Effect, I might explain that as, relative distances are distorted in the show. If one ship is traveling at different multiples of the speed of light they can still see each other slowly getting closer on the viewscreen. In Cause and Effect they didn't really need that much thrust to move clear of the ship. Let's say the ship needed to move 100m in 5s. The ship then needed to accelerate at 8 m/s^2.