Lord - Standard Single Lord, no problems for a circus of death.
Immortals - Assault weapons are great, though they really aren't all that superior to necron warriors, in a static or mobile non-circus of death battle line, they work.
Flayed Ones - I don't think they fit very well with the rest of your force, I suggest deep striking (or infiltrating, I forget which they have) to close the distance quicker, but expect them to die first, and be done, a small squad will mean that if they are killed to a man, they are gone.
Warriors - More warriors is always nice, but if your just sitting back with them and not being at all aggressive, you won't need to worry much about phase out... unless your opponent has indirect anyways.
Scarabs - Always a good choice, though you do have a lot of them, maybe break them down into 3 smaller squads for more manuverbility.
Heavy Destroyers - I've never been convinced of their effectiveness, You need to keep both groups near each other, else they will get wiped out and no WBBs for you. Granted, necron's don't have much choice when it comes to popping Termies or MCs, its still hard to use them. They also don't provide much weight of fire power and will provide little benefit against some armys, including orks and some Nid lists.
Monos - You can never go wrong with a mono, they are a pain in the ass to take down for most armies, and if you DS it right into the middle of a horde army, it will provide some good weight of fire, which I see your list lacking.
The important thing to keep in mind is that you must stay out of combat, even immortals won't stand up to any mid level assault element, and for all the guns are nice, I don't know if your going to have enough fire power to take out hordes, specially if you keep to your plan of hiding your warriors.
Keep the circus of death moving taking out important threats, and shield them with the loveable scarabs and make sure to use your monolith to recall for the rerolled WBBs, any casualties are going to hurt.
