honestly something more like this would work better

Necron Overlord- Phaeron, Staff of Light, Resurrection Orb (140)

20 Necron Warriors (260)

5 Immortals- Tesla Carbines (85)

Annihilation Barge (90)

Overlord into unit of warrior so they are more mobile and shootable and less likely to die due to res orb. Tesla Immortals can harass smaller units hopefully getting plenty of hits. Annihiliation Barge can deal with light vehicles and infantry. and you still have 25 points spare for some upgrades on the lord if you really want.