Spotting beyond the opening game turn LOS is a design feature and not a flaw. Even open terrain would have undulations inside the hexes that are less than an elevation change, but enough to obscure vision to spot an enemy in the next hex. Think low rolling hills like the steppes around Kursk.
The PzC & MC series are very offensive leaning game systems. Allowing the defense more than an a chance to remain in ambush mode behind their lines is really not too much to ask, IMHO.
Once you break through to open fields, have planned ahead to let a recon unit move through first and use recon spotting. Not 100% guaranteed the enemy will pop up and say "gosh darn you found me" but it is a way to mitigate moving in blind. Recon air is perfect for this situation also.
Fast is fine, but accuracy is everything.
- Wyatt Earp