Concept: 

If you max out a fleet with the highest logistics possible for the state of the game (ignore the Shrinker) and equip it with the best weapons (or the best weapons for that state of the game) NOTHING can stop it except for another similar maxed out fleet (assuming techs are approximately equal).  And if the two fleets battle each other, even the winner will be badly bruised and lose many ships.

Consequently, the concept of using "screen ships," or "scout ships" during a war is pointless.  A maxed out fleet is unstoppable, except by another similarly maxed out fleet. Furthermore, it doesn't matter if the maxed out fleet is surrounded and outnumbered by 10 maxed out fleets.  ONLY ONE OF THOSE 10 CAN BATTLE IT AT A SINGLE TIME.  

In other words, the optimal strategy in a war of attrition where one side has a major production bonus (but is unfortunately a tactical idiot) is ball up as many logistically maxed out ships as possible in a fleet, using the best technology possible.  And the best place to ball up is on your own home worlds near your shipyards (lowers the chance of the rallying troops getting picked off in transit.  Has the secondary purpose of protecting those worlds). Once you get the ball of ships in a gigantic fleet, even if the other side beats it, they'll take large casualties that will in the long run wear them down.  

Sending out scout ships in front of a maxed out fleet is actually a waste of resources.  Once a fleet maxes out logistically, there is nothing in the game of equivalent technology that can tackle it without taking large losses themselves.  In other words, for a tactically idiotic but extremely productive nation that is interested in waging a war of attrition, this is the best strategy BECAUSE IT PRETTY MUCH COMPLETELY AVOIDS TACTICS.  You don't need much tactics when you have concentrated numbers of ships.  

Think of the Stacks of Doom in Civilization III and IV.  Those things could be quite terrifying.  And I believe this is EXACTLY how the Civ IV developers envisioned it when they made the game.  They KNEW programming AI tactics was probably futile against an intelligent human, so instead they had the AI mass up these stacks of doom in SAFE PLACES (the reinforcements could not be picked off in transit) and then just charge them at you.

Civ IV AIs are idiots.  But they knew how to do one thing right: Concentrate the largest force possible IN A SAFE LOCATION WHERE THE INCOMING REINFORCEMENTS CANNOT BE PICKED OFF PIECEMEAL BY THE HUMAN PLAYER and then when the stack is ready, smack you with it.