As I said before, the Imprison set is extremely specific to those team that can afford dropping one (or both) Earthquake and Toxic. Most balance teams CAN'T have their Landorus-T miss even one of these moves; the only teamstyle that can afford this is HO and surrogates, where you don't need to click an uninvested Earthquake nor you need to Toxic a threat - you just need hazard and screen control against opposing Landorus-T, BOTH STEALTH ROCK AND DEFOG VARIANTS, with Stealth Rock + Defog + Imprison, and pivoting through U-turn. The statement in caps is very important - your HO team wants to keep its own Screens and Rocks up and deny opposing Rocks, which means having Imprison and both SR and Defog is VITAL. I don't see an Imprison set ever be worth it on a regular balance teams, where Landorus-T needs all its crucial moves.
On the topic of standard Landorus-T, I want to gauge the playerbase's opinion on
Protect. If your team can afford not running either SR or Defog on Landorus-T or don't particularly need Toxic, I feel like Protect is the next best option, moreso than Knock Off. Protect is very useful for many purposes:
LEFTOVERS RECOVERY = Landorus-T needs its Leftovers to keep it healthy, so Protect comes in handy to restore even more health throughout the game
SCOUTING = especially vs choiced attackers like Kartana, Tapu Lele, Dragapult, G-Zapdos and Weavile, being able to safely scout their moves can be absolutely game changing and help deal with them a lot more easily. Unfortunately, this doesn't work on Urshifu-R, though. It also helps baiting out random Ice Beams/Punches or Toxics on opposing Pokémon, safely revealing their lures.
TOXIC STALLING = Do I even need to explain the synergy between Protect and Toxic?
The spread can DEFINITELY be improved, but I don't have neither time nor mental energy to provide one atm, might do it tomorrow.
Anyway, I'm a bit skeptical on Smack Down in all honesty. There are two main reasons: first, a neutral Smack Down is weaker than a resisted Earthquake, which is pitiful. Secondly, many teams have more than one Ground immunity, which means that they can pivot around Smack Downs and Earthquake between their Ground immunities and Steel types. It may sounds wierd, but I actually like Gravity and Toxic a lot more, especially
Gravity. Opposing Landorus-T's Earthquakes now hitting you mean nothing when you can get 6 Bulk Ups in its face before even clicking Gravity. Gravity allows you to just click Earthquake on everything and avoids PP stalling scenarios from switches and even prevent Urshifu-R from switching in on a predicted Smack Down to threaten a Surging Strikes KO through Substitute.
That being said, Weavile's Triple Axel is a big threat to Sub Landorus-T and Weavile is the #2 OU mon, so keep in mind that setting up against Landorus-T ends up being very difficult when the opposing Landorus-T can just slow U-turn into Weavile (or Urshifu-R) that can KO you through Sub, so you absolutely need a plan B for these things (Toxic Spikes Toxapex sounds like a good partner).
What do y'all think about Protect SpD and Gravity SubBU
?