I suppose I should distinguish between long term defensive operations and short term ones.
When the deployment is expected to be less than 1/3 of the deployment time of the ships in question, sure, deploy them all forward. But otherwise maintenance issues are a big thing.
Basically, a forward defense allows a slower fleet with shorter ranged weapons to nonetheless choose the range of engagement.
So what if the attackers have 400 million km ranged missiles? Either they fire a lot of them at once, in which case the scout force just ducks back across the jump point, or they fire in dribs and drabs and they just get shot down by point defense.
You could have fighters with 20+ size 1 box launchers, 20-30 million km range, normally they would have no chance of getting in range, but they could launch right in the energy beam point defense envelope. Again, you couldn't normally get those slow point defense ships within 20 million km of the enemy fleet.
The tactical and strategic options for the defender in a forward defense are quite significant, and unlike the guard the door defense, they get to see the attacker coming.
I am sure that defenses made by a lower tech defender would be crackable, given time and research, but their odds of getting unopposed kills or simply coming out ahead on cost of a missile exchange are a lot higher with the option to withdraw. And they still have the option of a jump point defense. They could selectively target the incoming jump leaders, reducing the ability of the attacker to even transit.
Another defensive option:
Fighters with really long ranged missiles, sufficient that they expect to be untargetable at launch. Normally the issue is that such fighters are not going to be able to get multiple strikes that way, or carry enough missiles to kill an equal cost fleet. But they would be able to redock with their carriers after a trip of minutes, not hours, and reload to launch another large strike. And the carriers for such a role could be virtual barges, with nothing but hangars, fuel and ammunition.
You could have fighters that are almost nothing but missile launcher +fire control, virtually no engine, and they could still expect multiple strikes.
Another defense option would be to deploy very fast beam fighters once the attackers are within about 1 minute missile flight from the jump point. Such fighters might be rather short ranged, and normally not be capable of running down a fleet, not without exposing their carriers. If the attackers have 400 million km missile range, you couldn't have fighter barge carriers launch from a mere 400 million km and expect to be safe.
But launched with a jump point to withdraw behind? A crap ton of small fast fighters that are less than 10 minutes fighter flight from their targets?