Do one thing really, really well and force the enemy to react to you.
With the advent of 7th it makes it easier to cut out the weaker units that are filling the troops slot (especially in DE) though objective secured is incredibly good and DE's ability to get a lot of transports around quickly can really benefit them in Maelstrom of War missions. So try an weigh up the bonuses of that and if you can find an alternative go unbound and trying and push an armies strengths (though for unbounds to work you really need to be able to exploit it with at least 3+ of a power unit)
That's why I breifly mentioned it on this^ I wasn't sure what the DE ones would be so I ddin't mention it. But I personally think both aproaches work, as if you spam something like knights if the TO hasn't restricted the amount you can bring) or venoms, if your opponent has something that can easil counter it (e.g. crons in general and especially barges) you are going to die horribly.
Me: To be honest im amazed there isn't a chaos god of not revising or at least chaos god of procrastination
MidnightSun: There will be, when enough people do it. Y'know when the Eldar were all engaging in their hedonism and Slaanesh ripped open the Eye of Terror with his creation? Slaanesh will have NOTHING on the God of Procrastination, and his vile minions will carve the galaxy asunder in a thousand year reign of blood.... Tomorrow