Starfleet isn't 8,000 light years wide... that would take much too long for ships to get anywhere. That figure is 8,000 cubic light years... as 200 X 200 X 200. It makes more sense that way, as DS9 was on the outskirts, and the core was only 50 light years away.
I know the war didn't start at the same time as the Borg invasion, but the pact with Cardassia in "By Inferno's Light" was before the Borg "incident" so they knew it was coming.
200 cubed is way more then 8,000. One sector is 20 x 20 x 20 and that is 8,000 cubic light years.
Picard says something to the effect that the Federation stretched across 8,000 light years, which doesn't necessarily mean it is a perfect sphere with an 8,000 light year diameter but could just be the furthest distance between two Federation systems.
That's why you'd need a lot of starships to cover that with the current (2370s) state of ftl technology, which was the point I was getting at.
Nothing wrong with that and the location of DS9 because it was still at the edge (maybe beyond his it was in Bajoran space) of the Federation since it was on the cusp of the Cardassian Union.
How could the Dominion possibly know the Borg were going to attack the Federation when they did? Plus according to Deep Space 9, the attack occurred before the Dominion entered the Alpha Quadrant.
I prefer that then the later date of First Contact
as it is easier to believe that they would pull the Defiant
away from DS9 before the Dominion gained their foothold in the Alpha Quadrant. Then again a later date excuses the Enterprise
out of the early parts of the war due to the damage it received in the battle and having to de-Borg half the ship.