This is strange. Necrons outnumbering Tyranids? I am playing 50 power level vs. 2x 25 power level detachments. My army list via Battlescribe is as follows:
Dynasty: Mephrit
Cryptothralls [2 PL, 40pts]
2x Cryptothrall: 2x Scouring Eye, 2x Scythed Limbs
Overlord (Indomitus) [5 PL, 90pts]: Is a Custom Character, Warlord, Warlord Trait (BRB): Inspiring Leader
Plasmancer [4 PL, 80pts]
Skorpekh Lord [7 PL, 130pts]
Necron Warriors (Indomitus) [6 PL, 120pts]
. 10x Necron Warrior (Gauss Flayer): 10x Gauss Flayer
Necron Warriors (Indomitus) [6 PL, 120pts]
. 10x Necron Warrior (Gauss Reaper): 10x Gauss Reaper
Necron Warriors (Indomitus) [6 PL, 120pts]
. 10x Necron Warrior (Gauss Reaper): 10x Gauss Reaper
Canoptek Reanimator [5 PL, 110pts]
Skorpekh Destroyers [7 PL, 135pts]: Plasmacyte, Skorpekh Destroyer (Reap-Blade)
. 2x Skorpekh Destroyer (Thresher): 2x Hyperphase Threshers
Canoptek Scarab Swarms (Indomitus) [2 PL, 45pts]
. 3x Scarab Swarms (Indomitus): 3x Feeder Mandibles (Indomitus)
Not winning. Scary alien monsters are scary, even when you are a robot zombie army. I didn't bring the right units to handle an army of Hive Tyrants, a Lictor, a Trygon Prime, Hive Guard, and Warriors. The only usual troops they brought was ripper swarms.
Lessons learned: be more defensive. Focus on objectives. And buy some models who can deal with multi-wound monstrosities.