" Does the red line problem stem from poor map design? "

No.
redline is a safe zone.

dusty's will always exploit suits, weapons, maps, redlines, etc. to there fullest potential towards OP.
It is the nature of the game.

The primary problem with the red line is that players can affect the battle, sometimes strongly with a relatively small chance of retaliation. My preferred solution would involve removing the red zone entirely. However perhaps there is another solution. Perhaps the issue is less with the red line itself and more related to the map design.

What if the maps were designed so that there was no direct line of sight from the initial spawns into the combat zone? The red line would still exist as a staging area, but there would be no chance of a rail tank or sniper exploiting red line mechanics for easy gains.

This flies in the face of recent maps with a tight red line or the crater maps so common from the beta. In fact, the line would be moved out quite a ways, or hills would be placed between the combat zone and the red line. This would slow the initial push, but larger maps that better leverage vehicle logistics would be a plus in any case. Add this alongside 32x32 battles, and you might just have a solution to annoying red line tankers and snipers.