Its not a matter of the Nightbringer and Monoliths not being able to do their respective jobs... its a question of the enemy getting into Close Combat with your Warriors fast enough and hitting hard enough to break the units and force a Phase out.
I have already faced Necorns at 2K with 2 Mono's and the same sort of concept (Basically your list with 1 less mono, 1 less Destroyer squad) and My Wildriders took a whole 4 turns to take him down to 5 figures total (his PO was = 11 but he said he wanted to see how long he could last, so I used turn 4 to kill more stuff and drop the Monoliths too). By simply avoiding the Nightbringer (whom I think rocks) and/or the Mono's until your ready to deal with them, a smart opponent will phase you out. What you need is "Speed Bumps" and a single unit of Scarabs does not do it....
I am not saying that you couldn't win vs my style of army, or the others I listed... what I am saying is that they will focus on PO, so you better be ready for it. They can also be as fast as lightning and tough as nails, so there is often not much Necron shooting time to widdle them down... Remember that I too play Necrons (and I am doing well with them). I would suggest that you drop 1 Monolith and get a decent squad of Immortals for use as Drop in shooters or Close Combat speed bumps, and they increase your PO number while you would still have 2 Monoliths to set up blocks, etc.... Even better, drop the Mono and the Scarabs and get 2 squads or 6-7 Immortals to augment you shooting, provide speed bumps, and boost your PO number, more options all around.
PS... what do you plan to do vs an army with multiple Armour...such as Mech Eldar, Mech SM/CSM, etc... as your Glancing will slow their shooting; but the CC troops will still get to you.
PPS... Your calling me "Son", well at 41 yrs old that would put you up around 60+ or so... so if I'm ever in New Hampshire, I will look you up at the seniors home and give you a game. (no disrespect to anyone older out there... this is friendly banter between us.. LoL)
CaHG