Teams Ghost Weakness is over-exaggerated. The combination of Toxapex and AV Mag, although should have more spdef to me personally, offsets the Gengar matchup and if we're talking about Alolan Marowak someone would have to play aggressively to get in on the passive mons which I would assume Indigo would see from team preview and play accordingly. If anything Indigo has to worry more about Zygarde SubCoilDance Variants, Volcarona which was already mentioned, and Stall. Any decent stall archetype with the combination of M-Sab, Chansey and friends probably isn't going to care too much about this team outside of major chokes and misplays. The big thing that is overlooked is the weakness of Spikes, a lot of times people build on the concept of not being rock weak and complete ignore or don't account for the Spike Weakness which can be worse long term against teams such as this.
T-Spikes over Toxic on Toxapex can alleviate some of these matchups but overall those are the big issues on paper.
For the sake of throwing something out there that's going to hurt this team here's a basic one to establish the Spike Weakness.
Greninja @ Focus Sash
Ability: Protean
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Toxic Spikes
- Spikes
- Taunt
- Ice Beam
Any Ninja set with Spikes can work but seeing as this set can guarantee a Spike or Two with minor issues I figured would be the easiest to showcase.