Claimed to be the rival of Hoenn's savior, Rayquaza, Nostratos is an interesting pseudo-legend, in its own right. In fact, it does share many traits to another Dragon/Flying Pseudo-Legendary: Salamence (Unless if you factor Mega Salamence in the equation). However, the only major differences are that it has higher Special Attack than Salamence and a 1 Point better Speed that outpaces the 100 Speed tier. With outstanding attacking stats on both fronts and speed, the Grand Dragon excels as an offensive powerhouse with ease with Draco Meteor and Typhoon. Possessing the coveted Baton Pass, Nostratos can also be used as a Baton Passer (Something that sets apart from Salamence in the support department outside of Defog) thanks to its plethora of setup moves such as Dragon Dance, Nasty Plot, and Agility along with Intimidate to grant setup opportunities with its Ground immunity.
However, the Grand Dragon still has a few cons:
1) Nostratos's overall typing is not the best defensively, especially when compared to its pre-evolutions' amazing dual typing of Dragon/Water, which is only 1 Weakness: Dragon.
2) Nostratos's defenses, while respectable, are a bit weak, especially for supportive roles. Although, its physical defense is heavily cushioned by its Intimidate.
3) Nostratos's movepool, while decent, could be better. Raze Earth, Raging Flame, Heat Wave, and Focus Blast would have been awesome to have. Typhoon is a risky Special Flying STAB to use due to the random buffs and debuffs, especially without Choice Specs or Life Orb to boost its damage output further, even with Nasty Plot.
4) Other Pokémon that share one of Nostratos's types can perform its roles much more efficiently, thanks to their wider movepools, stats, and/or abilities, even though Nostratos does very strong work with Nasty Plot sweeper. (EX: Mingola (With its signature held item, the Pink Soap), Latias, Latios, Blizentork (Huge Power, despite the amount of weaknesses), Gatanoia, Roytsar, R'Duckulus, Ganimede, Coruda, Komoragon, Conductot, Pteriarch, etc.)