at the moment I simply 'Deploy to a line' then order an 'March to an area' to where the enemy is located.
That's pretty much how we used to do it in ANGV: deploy in line facing the direction you want to attack, then order an advance and let the units figure out where to stop and fire.
It's not quite the same here, as Count von Csollich explained above. The main thing here is that the "march to area" order doesn't keep formation, but has everyone moving independently at their best speed. It may be useful for getting a corps to a new location in a hurry, but it's not a combat formation.
When you give a Deploy order, it covers both the initial deployment and the movement to contact, all of which is handled by the corps commander, and the units move in a combat formation. They will also halt for artillery preparation if they encounter enemy resistance, and may retreat and regroup if necessary.
Something to remember: Both march to area and defend on line will have the individual units move directly to their final positions, without supporting other units in the corps. It's only the deploy and diversion orders that moves the entire corps in a proper formation for combat. If you wish to form a defensive line somewhere deep in enemy territory, it's better to give a deploy order near where you want the defensive line, then issue the defensive line order separately for execution after they arrive. They usually form defensive line automatically if they have no further orders.
Hook