Hello, whilst I was also thinking that Sheer Force Landorus could be good in ORAS Ubers, some of the examples you have posted are wrong and show that you might not have the most up-to-date knowledge of the tier. At best, Landorus can beat things if they switch in, but cannot switch in on anything safely at all, meaning that it is a very poor check to many of these Pokemon
- Aegislash will be running full Special Defense and a Sassy nature to take on Latios, Latias and Xerneas, and would not be staying in anyway.
- Lucario will outspeed you once it has Mega Evolved and can pick you off with Bullet Punch
- Blaziken can just Protect against Landorus and then murder it with Flare Blitz
- Deoxys-Attack will promptly OHKO Landorus with Psycho Boost or Ice Beam
- Deoxys-Speed will set up its two layers of hazards happily
- Mawile is probably a shaky case when it comes to even being viable
- Zekrom can easily be Scarf or Tailwind, outspeed and OHKO Landorus
- Arceus-Normal will almost OHKO with Extremespeed, Arceus-Dark will Calm Mind on Landorus or just Judgment it, Arceus-Electric will promptly OHKO with Ice Beam or Blizzard, Arceus-Rock will be outspeeding and will deal severe damage with Judgment, Arceus-Fighting is unviable, and Arceus-Poison has drastically dropped in usability.
- Kyurem-W will most likely be Scarf and will promptly OHKO with Ice Beam
- Darkrai will Dark Void, then KO with Dark Pulse after Bad Dreams damage
You're forgetting that Lati@s are in the tier, and are extremely competent checks that are further bolstered by Soul Dew, you can hit them with Knock Off but that's not the most reliable solution
You will also be using Primal Groudon on your team so you will have to justify using two Ground-types, although in this case they are different enough that it is not really a big deal
Support Arceus are not 2HKOed by Earth Power and can burn Landorus before Recovering any damage away
A wide variety of Pokemon outspeed Landorus and can OHKO it. Giratina-Origin does not care in the slightest about Knock Off and can easily shrug off a Psychic, offering an OHKO with Draco Meteor in return.