GR: Is getting your build order down to a science important, or does the player need to be flexible according to the race that is being played against?
Josh: In DC, exact build order doesn't seem to matter much. Players should stick to their own build order, but it should not be exactly the same every game. For example, when using a fast teching build order with Necrons, it is important to adjust the number of Necron Warriors, power generators, and so on, depending on the situation. For example if the other person is teching up quickly, you would build the free Necron Warrior squads, but not reinforce them, whereas if the other player is massing tier 1 units, it will be wise to add a turret, and/or reinforce some of the Necron Warrior squads.
Stephan: For the typical player, experiment to find out what works for you. But observing online battles to find out the build orders of advanced players is about the best advice I can give you. Intermediate/casual players will typically look for set build orders, which can work to an extent. However, at the advanced level, varieties of build orders are created to counter the race one is facing, and the opponent himself, and adapting to what they do.
GR: What about having more than one enemy - what changes strategically for players in that situation?
Stephan: When facing multiple opponents, all factors are generally multiplied. Massing can be stronger due to the sheer number of units brought to bear on base structures, and thus greater "pressure" can be applied. Conversely, team games tend to go on longer, thus the effects of teching can also be amplified. Team play focuses more on communication and planning as opposed to execution, and will teach more overall game dynamics than simply playing one-versus-one exclusively.