it doesn't have to go to BL prior to going to OU, which is he case of Umbreon.
If it was used (not TOO sure of exact numbers) at least once out of every 20 games for about 3 months (?), it wil be OU.
As for Missy...I was thinking about using it as well but whih set do you think is the most effective? Ovrall ofc lol
As a sweeper Nasty Plot + 3 attacks works fine, Nasty Plot + Taunt + 2 attacks works well too since if you use 3 attacks, chances are you're using Hidden Power.
For a Raikou-ish approach, you can use Substitute + Calm Mind + 2 attacks, or a personal favorite, Substitute + Taunt + 2 attacks.
For a spinblocker approach, try this set:
@ Leftovers
Shadow Ball
Taunt
Will-O-Wisp
Protect
Timid / Calm
If using Timid: 252 HP / 192 SpD / 64 Spe
If using Calm: 252 HP / 88 SpD / 168 Spe
Levitate
Spin-blocker. Yeah. Forretress
always loses to you if you come in on the Spin, as a combination of Will-O-Wisp and Taunt neuters it. With Mismagius' fantastic Special Defense, Tentacruel will not break you either. Starmie, unfortunately, can 2HKO you if you predict wrong and it's not a Rapid Spinner. (Trick to find out if it's a Rapid Spinner: only Starmie set that uses Leftovers) That's not really surprising as Life Orb Starmie 2HKOs Rotom-A as well. Anyway, when you get in, you can scare it out with the threat of a 2HKO whereas Starmie cannot even 3HKO you.
Outside of the Spinblocker position Mismagius, once the foe realizes the lack of Substitute, is sure to bring in Scizor or Tyranitar. Here's where Protect comes in: it's an easy scout: if they use Pursuit (or U-Turn, in Scizor's case), they are a) crippled with Will-O-Wisp, b) taking damage from your entry hazards (you are using Spikes w/ a spinblocker, right?), or c) taking damage from your entry hazards and allowing a teammate to be Burned. If they use Bullet Punch (or Iron Head, in Scarf Scizor's case; Crunch, in Tyranitar's case), you can easily switch to Skarmory, the best Spikes-er in the OU metagame, and set up Spikes. If they Dance, Skarmory still wins as long as Scizor lacks Superpower, but even then, a very Physically Defensive Skarmory can survive and pHaze it out.
If Gyarados gets courageous and tries to setup on you, you outspeed Jolly +0 Gyarados and may Taunt it, followed by a swift burn. They'll probably switch out, but that's -50% from Stealth Rock right there. As you outspeed Gyarados, you also outspeed Dragonite, but be EXTREMELY CAUTIOUS it will not Draco Meteor you (personally, I would Burn it, not Taunt it, first, as Skarmory would still be able to pHaze it out, and Mismagius is not OHKOd by Draco Meteor (-2 Burned Dragonite is similarly handled by Skarmory.) Adamant Kingdra is outsped as well.
tl, dr; spin-blocker, beats all Rapid Spinners in OU, beats Choiced Scizor or Tyranitar, cannot be setup on by the likes of Gyarados, Dragonite, or Kingdra, as well as hitting hard with a respectable 246 Special Attack.
Edit: No, I
don't want you to use Spin-blocker Mismagius, I just wrote, like, 20x more about it than the other sets. Because I can obviously cope with it in UU. /sarcasm
Edit 2: Rosie went straight to OU, past BL, as well; BL is if you get
voted overpowered, not if your usage is overused