It should at least be UU. I've never seen a Pokemon that can effortlessly sweep as many Pokemon in UU/OU, even with maximum defensive investment and with as much safety as Minior. Maybe BL if the priority in OU actually turns out to be a problem. But consider that:
-There is a lot of priority hate this generation, so we might be seeing it less, especially if Bruxish and/or Tsareena end up being used much.
-Only specific Pokemon hold Bullet Punch/Ice Shard and are VERY well known for their doing so. So well known you can write a list of them without referring to any actual movepools and then choose checks or counters to support Minior.
-None of the new Pokemon are fast, so uninvested Minior outspeeds an even wider blanket of the game than before.
-Seriously, nothing except like full defense Lunala (252 HP/0 Def isn't enough) and mega Aggron can actually switch in on Minior. If you get rid of priority users, your Minior has a good chance of taking their entire team down unless they use Focus Sash/Sturdy which are both not super common.
Immunity to spikes and ground are good. And also its Stealth Rock weakness is a double edged sword. Rather than being purely bad for Minior like any rock-weak Pokemon, now attacks that do 25-74.9% will put you in range for the sweep instead of 50-99.9%. It opens up many other possibilities that we still have 256 leftover EVs to make happen. They don't all have to go into spatk. We can put just enough in HP so that with 100/100 defenses it reaches unarmored form safely more often than otherwise.
-There is a lot of priority hate this generation, so we might be seeing it less, especially if Bruxish and/or Tsareena end up being used much.
-Only specific Pokemon hold Bullet Punch/Ice Shard and are VERY well known for their doing so. So well known you can write a list of them without referring to any actual movepools and then choose checks or counters to support Minior.
-None of the new Pokemon are fast, so uninvested Minior outspeeds an even wider blanket of the game than before.
-Seriously, nothing except like full defense Lunala (252 HP/0 Def isn't enough) and mega Aggron can actually switch in on Minior. If you get rid of priority users, your Minior has a good chance of taking their entire team down unless they use Focus Sash/Sturdy which are both not super common.
Immunity to spikes and ground are good. And also its Stealth Rock weakness is a double edged sword. Rather than being purely bad for Minior like any rock-weak Pokemon, now attacks that do 25-74.9% will put you in range for the sweep instead of 50-99.9%. It opens up many other possibilities that we still have 256 leftover EVs to make happen. They don't all have to go into spatk. We can put just enough in HP so that with 100/100 defenses it reaches unarmored form safely more often than otherwise.