No, TR SD NDM is not that great because of Ho-Oh which literally walls the whole set.
Back in USUM, there were no Heavy-Duty Boots and Dynamax. Due to this, Searing Sunraze Smash could OHKO Ho-Oh at +2 after Stealth Rock damage. However, with the addition of Heavy Duty Boots, Ho-Oh isn't affected by Stealth Rock, and Z-Moves are worse and harder to fit because of Dynamax.
+2 252+ Atk Necrozma-Dusk-Mane Searing Sunraze Smash vs. 252 HP / 204+ Def Ho-Oh: 332-391 (79.8 - 93.9%) -- guaranteed OHKO after Stealth Rock
Ho-Oh is very common in Nat Dex AG which becomes troublesome for Steel-Quake combo Necrozma DM, as it can tank hits easily thanks to its defensive, typing then threaten to burn with Sacred Fire or even Whirlwind to phaze your boosts.
Even though you can run Stone Edge over Swords Dance for Ho-Oh, it makes it easier for physically Defensive Necro-DM, WaterCeus and Primal Groudon as without getting struck by a super effective hit and no Swords Dance, you can't literally touch them due to their super fat bulk and typing.
Right now in Nat Dex AG, you often would see Dragon Dance Necro DM or Ultra DD sets. This kind of movesets can save one moveslot by combining Rock Polish / Trick Room + Swords Dance into one single Dragon Dance which makes them harder to revenge kill as well as get additional coverage. Here are the sets for both:
Necrozma-Dusk-Mane @ Life Orb / Weakness Policy
Ability: Prism Armor
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Dragon Dance
- Psychic Fangs / Stone Edge
- Sunsteel Strike
- Earthquake
Necrozma-Ultra @ Ultranecrozium Z
Ability: Prism Armor
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature / Jolly Nature
- Dragon Dance
- Photon Geyser
- Stone Edge
- Earthquake
What are some good partners for them?
Defensive partners: 
Offensive partners: 
Running an offensive Necrozma-Dusk-Mane means you're forgoing massive defense utility for checking Zacian-C and Xerneas as well as Stealth Rock. Primal Groudon can solve that problem very well, as well as set-up Stealth Rock. It also handles Primal Kyogre, which is a threat to Non-Ultra sets as it can live unboosted Earthquakes very well, and threaten to OHKO back with Water Spout and Origin Pulse.
Calyrex-S is also an issue, so to solve it Yveltal comes to the rescue. It can also force Choice Locked Ditto into Earthquake once Dynamax is over, so it's a nice Imposter-proof as well. Finally, Zygarde-C can completely wall Ditto transformed into Necrozma-Dusk Mane and provide speed control with Glare as well.
Offensively, Xerneas pairs well, as it threatens Arceus formes like DarkCeus, WaterCeus and GroundCeus as well as Zygarde-C which wall Dusk Mane. In return, the latter deals with Chansey and Zacian-C. Primal Kyogre meanwhile threatens out pretty much every of its counters and each pressurize Primal Groudon well. Finally, Zacian-C can take advantage of opposing weakened Dusk Mane, Primal Groudon and GroundCeus while also threatening out Yveltal.
That's all, hope I helped :)
