Apart from the fact that the Destroyer Lord is too tough to be IDed by the SwarmLord.
I would generally try to lock Necrons in CC asap. They are not helpless in CC, but they are worse at it than shooting so that is your best chance.
Outflanking Genestealers is solid, depending on the enemy's choices regarding terrain manipulation.
A Hive Commander that lets you outflank the Warrior unit might also be useful instead of the SwarmLord.
If you go shooty then volume of fire will trump high-S shots vs Necrons.
All that is important is known.