I decided to go with the Archon+8 wyches + haemonculus loadout. I played a game vs. Necrons. The Archon/wyches assaulted my opponents destroyer squad (I figured that I really needed to wipe out his destroyers first , as they had the potential to cause me some serious pain). However, on the first round of close combat he managed to pass LD check (at -4) and 3 of his wounded destroyers got back up. During the next turn, he charged a full unit of warriors into the combat. I still won combat, and the destroyers fell back... but the warriors passed their LD check, preventing me from sweeping the destroyers. Eventually, massed attacks shorted out my shadowfield, making the archon vulnerable to a death scythe hit later on.
So.. next time: I shoot the crap out of the destroyers, and charge either his lychguard or his praetorians instead.
Ended up a tie game, with all 3 objectives contested.