Your PO is 9 so as your opponent I would concentrate all my efforts on just four units: Immortals, 2xWarriors, and Destroyers. Taking out these units will force you to phase out. With only four units to worry about, my tactics are just that simple, ignore everything else but these four units. Worse, what happens if these units come in piecemeal? I can focus more of my army on what units do come in.
Two of these units suffer from now WBB capability: Immortals and Destroyers. I would target my range weapons on these targets. My CC capable units will attack your
Warriors. With luck, I will sweep them in one assault phase.
Some thoughts:
If you're running with two units of Wraiths, build a Destroyer Lord with Phase Shifter, ResOrb, and Warscythe, attach him to one of the units of Wraiths and run both Wraith units in tandem. I've found this combination to be extremely potent particularly if a Monolith is near by and can be used to pull a unit of Wraiths out of CC.
Pariahs look good on paper but I just haven't seem them be useful. They have a great weapon but are slow and have few attacks. I'd be surprised you get them into CC before being phased out. I think more Immortals would be more beneficial.
Either go with Wraiths or go with Destroyers. Because of the necessity of redundancy due to WBB, just one unit of Destroyer (especially just three models to the unit) is extremely vulnerable. Destroyers work well in larger units with WBB support. A single unit of three will die in the first round of shooting.
The Nightbringer and Monoliths are fine at this level of points. I just thing you need to work on the rest.
A suggestion:
1 Destroyer Lord with Phase Shifter/Orb/Warscythe - 210
Nightbringer - 360
2 x 10 Immortals - 560
1 11 Warriors - 198
1 12 Warriors - 216
2 x 3 Wraiths - 246
3 Monoliths - 705
Total - 2495
PO 12
