I can tell you you can forget about taking 2 Despairteks with Veil, since you only have 1
HQ. Trust me I wish you could, cause it's just a beautiful piece of equipment.
Since you can't do that I would drop 1 cryptek and give the Immortals that don't get the cryptek with veil Tesla instead of Gauss (since you lose the benefit of the rapidfire from the gauss when using the Veil to get in close range)
Also I would definatly try to get (at least some) Wraiths in the list, Fast Attack is the Necron's best slot, use it to the fullest.
Also instead of using an Overlord with
CCB take Obyron. You can't take the 1x cryptek with veil also then, but Obyron can do what that cryptek can, only better (you can even use it to get out of close combat then) and for less points when you count all that up. Only downside to this would be that you'd have to keep Obyron with the squad of gauss Immortals, but you can teleport from vehicle to vehicle, destroying everything without any problems whatsoever (20 shots of gauss when within 12" and a warscythe to finish up in close combat should it be necessary)
Hope it helps.