As I see it, Sand in SV is very, very rare. There is no Excadrill to abuse Sand, Lycanroc is underwhelming (wait you don't even have Lycanroc), and Great Tusk is a body to literally most of the team. Instead of going over the individual Pokemon, I feel like the strategy overall needs a big overhaul. Lets point out the main flaws:
Cleanup Potential: There are two "cleaners" on the team: DD Ttar and Gholdengo. However, DD Ttar is bodied by, you guessed it, Great Tusk, while Gholdengo's perk is its speed with scarf, which, while able to clean up a weakened team, comes with the condition that the team must be weakened first. Not an easy task with this team.
Defense: There is no reason why the combination of Great Tusk and Iron Valiant can't steamroll through this team (or do massive damage). Tusk can pick up a Rapid Spin on many passive mons on the team and bowl over everything except for post-tera Garg, Corv, and Hippo. Valiant's Thunderbolt handles the first two, and its strong Moonblast hits Hippo for tons of damage. If Hippo opts to Tera Fire, fine, get nuked by Tusk. There are also numerous other threats to this team, such as Samurott-H, which can pack Sacred Sword for Garg and Ttar, and Greninja, largely for the same reasons as Samurott-H, but also packing Grass Knot for post Tera Garg.
With the weaknesses listed, now let's try and remove these one by one.
Cleanup Potential: The only way to make this team semi-viable is to stray away from the Sand theme. Remove Hippowdown - its far too passive. Instead, use Kingambit (all Pokemon I recommend will have sets at the end of this answer). Gambit has great cleanup potential with its potent Sucker Punches boosted by Supreme Overlord, and its Priority helps with potential revenge killing issues that this team may run into.
Defense: This Corviknight set needs to change. Corviknight specializes in spamming roost and sitting on opponents, and the current set does not achieve this goal. Remove the AV and put in Rocky Helmet for physical chip. Use a moveset of Body Press, U-Turn, Defog, and Roost. This allows for hazard removal along with some offense and pivoting. Shift your EVs to max out HP and Def (last 4 in Atk), and go for a +Def, -SpA nature. Use pressure as the ability (Mirror armor is far too situational, and Intimidate doesn't affect is as much now that its only using Atk for U-Turn). To handle the Electric weakness, simply go into Scarf Gholdengo and fire a Make it Rain. It'll do big damage to anything.
Other Suggestions: Trick on Gholdengo over Psychic provides better counterplay against stall teams, as it allows for a member to be permanently crippled. Opt for a bulkier set on Ttar (I'll provide one) as dragon dance doesn't allow ttar to do anything of note in this Tusk-infested meta.
Kingambit @ Black Glasses
Ability: Supreme Overlord
Tera Type: Dark
EVs: 252 Atk / 116 Def / 140 Spe
Adamant Nature
- Sucker Punch
- Kowtow Cleave
- Swords Dance
- Iron Head
A more offensive Kingambit variant using Tera Dark and Black Glasses. 140 Speed Evs outspeed Corviknight, and the rest is dumped in Defense. Pretty self explanatory, this is meant to clean up if all else fails and act as an emergancy setup sweeper check.
Tyranitar (M) @ Assault Vest
Ability: Sand Stream
Tera Type: Flying
EVs: 252 HP / 252 SpA / 4 SpD
Modest Nature
IVs: 0 Atk
- Ice Beam
- Dark Pulse
- Thunderbolt
- Earth Power
Special Ttar is one of the few ways it can do some sort of damage. Ice Beam hits Tusk, Thunderbolt hits Pex, and EP hits Heatran. Assault Vest makes the most of the Special Defense Boost, and Tera Flying Ensures that there is some defensive counterplay when it comes to tabling the turns on a weakened Iron Valiant.
I'm not the most familiar with sand, and so I don't know if my suggestions are completely accurate to the meta. However, I hope I gave enough suggestions to net some more success with this team on the ladder.