In these battles we are fighting, we are always heavily outnumbered, that's what makes it fun. This makes it almost impossible to deploy across your front to match superior enemy numbers; if you try to, you often leave yourself without sufficient reserves to counter attack. My basic tactic when outnumbered, is not to try to cover the whole front Corp for Corp, but to use the topography of the battlefield to create a defensive strategy that uses the minimum amount of troops to defend, so leaving enough troops for a counter attack. This usually means "Refusing" one flank or the center because you don't have enough force to cover all and keep a good sized reserve. I will use one or two reserve Corp to counter any attack in the sector of "Refusal", this usually leads to my counterattack developing. If the enemy doesn't attack my sector of "Refusal", then so well and good, he must be attacking my defense lines which leaves me to use my reserve at will, usually against a weak point that will give me a route to his LOP. I will usually use my OG at this stage, linking in support of a successful attacking Corp.
This whole strategy often leads to much reassignment of units during initial deployment. For instance, there isn't much point in having half your heavy artillery sat behind the lines for half the day so my outnumbered Defense Corp have a large disproportionate number of artillery reassigned to them, they may be outnumbered but they often have artillery superiority.
Similarly my reserve Corps are going to be moving quickly across the battlefield engaging and pursuing the enemy so I make sure they have Horse Artillery for this purpose. I can't cover every thing I do, but this is an outline. Hope it's of some help.
HistWar (English zone)