Welcome to Librarium Online!
I just got my Warrior Phalanx in yesterday (I'm super stoked, and debating where to even begin) and I've been contemplating an army list without a Monolith in it for the 1500pt. games I play over at a friends. I'm still thinking over what I want in it, but I'm thinking beefing up on Flayed Ones and Scarabs will help with CC, and some Destroyers would help with anti-tank. I'll probably stick with a Lord with a Rez Orb and (if I can fit them in) a Tomb Spyder or two, so that I have a much better chance of not having my WBB denied.
I'll probably be fighting Orks and IG, and then I think Tyranids and Chaos Daemons will be entering the fray as well very shortly. I'm mostly just curious if a list like that will result in me being completely slaughtered is all (I play for fun... but having your army not even make a dent in the opposing force is not an enjoyable process), or if I stand a decent chance of posing a viable threat (not necessarily winning).
unfortunetly, of the armies you list all of them are spectacular at assualt (barring IG mind you they're just shooty) and most if not all of the necron assualt units will fail against these armies, then pretty much all of the shooty necron units will fail to assualts
Necrons are best at shooting and should avoid assualts as much as possible, espacially in 5e. With the new sweeping advance loseing by 1 wound can result in the whole squad being wiped out and with such a low inititive, failing morale almost garentees getting sweeped and we won't get to use WBB
if those are the armies you'll end up playing against you should be going almost pure shooty and you want as much fire power as you can get so lots of warriors and destroyers. It also is useful to get a monolith to pull necrons out of the assualt to keep them safe
Toss a list up in the army list subforum
Anti CC I suggest Lord w/ res orb and Chronometron, Tomb Spyders and scarabs myself. Flayed ones aren't bad, just not fantastic, they're a specialist unit for anti shooting squads.
Monolith is by NO means necessary, it's just one of the ways to deal with assault, not the end all, especially with sweeping advance the way it is.
Necron armies, especially in the 1500 point range, are still very effective even without a Monolith. Since you can't rely on the Power Matrix to get re-rolls on your WBB, make sure every Necron unit makes full use of the Lord's Res Orb.
Thing is, the armies you listed (Orks, 'Guard, Tyranids) tend to be full of troopos with (usually) low Save and Toughness. The Gauss Flux Arc really excels at decimating squads of these units, especially if the 'Lith is dropped straight into the middle of the enemy early on.
I'd enhance your list with (at least) 4 destroyers and 3 wraiths. Scarabs could be also used to slow down the enemy. I also suggest to count on a large number of warriors (30-40 warriors fielded as you choose)
Instead of pariah use inmortals, they are cheaper, not that reliable at cc as pariah, but let 'em shoot those weak aurmours of your opponent before he reaches to assault your units.
Basically what I'd do is wait and shoot using destroyers to concentrate fire upon an enemy unit. Use them wraiths to hold the line and defend your troops if he reaches to assault. Your leader should be near the combat but not in it, Res Orb is more important than the cost of the leader itself. (remember phase out) Try to combine res orb + wraiths (sv 3+ inv).
Thanks everyone, the input was much appreciated.
I'll post an army list soon, I've been swamped lately and wasn't able to get to it. We've been playing 1k point games lately because of the spike in participants, so it'll be two lists actually, which I think I could base a 2k point list off of if I wanted.