This can be fixed ahead of time with iterative testing. Finding retreat paths from all areas of the map is a must for any competitive map. Big maps just take more time to find all the paths thats all.
I dont think its a major issue, just another design element of any map.
I'm not talking retreat paths, I mean at a certain length pathfinding just starts bugging out. Pathing will stop calculating for objects, and often times the unit will just stop a portion of the distance because the original command was too far.
In fact I think retreating is the only thing that tends to not break pathing over distance.
(Also, this reminded me of how shift-commands are buggy as hell.) But I have to say I have not taken the time to specifically test for this, this is only a perception of experience, and based on how the WorldBuilder's ruler is broken to hell and demonstrates a similar pattern.