I probably would not use cores if Pather cells worked, if only to reduce the babysitting required. My fleet, with burn 20 and Navigation 3, already runs around like a chicken with its head cut off juggling with pirate raids, expeditions, and whatever limited free time I have in the meantime to do whatever I want. I do not need even more things that I need to kill and add to the babysitting burden.
If I do not use cores, I build my colonies so that interest never exceeds 6. Without cores, I do need colony skills to get enough worlds and Industrial Planning.
There should be a way to permanently remove the Pather cell threat. In one game, I prevented Pather cells from appearing at my colonies, and could plant as many alpha-run colonies as I wanted without Pather cells appearing, but I have not figured out exactly how it happened. I decivilized every world owned by a major faction when that happened. (No Hegemony, no more inspections. Removing Hegemony alone did not stop Pather cells from appearing.)