tactic wise im not sure what your plan is, form what i can see this is what i reccon. The Ressurection Orb, Tomb Spiders and Monolith work together to make your army HARD. Flayed ones can pop up and attack enemies rear, tanks and heavy weapons. The Nightbringer will absorb the brust of the firepower, with any luck allowing the wraiths, scarabs and destroyers to move about freely. You do seem to lack firepower though, 3 destroyers are the only good mobile support, static firepower in warriors is ok, but a little short ranged. You look to be moving more towads an assault necron army that is resilient. The mass of warriros should stop phase out.
RESILIENCE: 10
FIREPOWER: 4
ASSUALT: 6
Improvements:
The Lords looks to be trying to fufill too many roles, either use him to augment necrons or as a lead assault unit. Nightbrignger, fine. Flayed ones ok. Warriors, enough. Wraiths, in the open they are too vunerale to shooting, they have to be hidden by the warriors, who are slow moving, using 3 to protect your warriors from assault is better than leading the assualt. 3 Destroyers can be killed VERY easly, once they are they cannot come back, i would reccomend you take more of these MINIMUM of 5 in a squad. Scarabs can protect your warriors or act as the lead assault units, whateva you do i would take 10, make it night impossible to kill them all, then you can hold up the enemy in assualt. Monolith, personally i do not think it is worth the points, it is too risky getting killed, and 235 point to fire a demolisher cannon some of the time, NO! In a game you will not make back the points value of this unit back either by shooting or re-phasing units from it. Take at your own perel. Tomb Spiders, hmm, still unsure about these little babys but as a ruke of thum spending the points on a staff of light on a unit with BS 2. Not really sensable.
The most nasty necron tactic I have seen are 10 Immortals, Lord, Veil of Darkness and Ressurection Orb. Impossible to assault, kill and so much firepower. With a tomb spider nearby, and another sqaud of immortals behind some warriors, even if you kill the entire squad, UNLIKLY. Then you can still use we'll be back! Then teleport out of the way.