Hmm, you do all have points. Ok, I give up. It seems that Mewtwo CAN be pawned by some Pokemons. And with their expected Movestes at that. Still, do not underestimate the fact that Mewtwo keeps on having an excelently balanced offensive set of stats (High HP and decent defenses). BUT, like I said, Mewtwo can appear with quite the unexpected MoveSet. And, besides, do not think that a serious trainer would step on all those traps that easily. In a 6-member team there's gonna be 1 Mewtwo killer. And that is due to the fact that you are not gonna use 3 Deoxys in a team or teaching all those sophisticated and specialized MSes on ALL your Pokemons!!!
So the opponent could always switch to something else and keep mewtwo to eliminate the rest of the team. In ANY case, in ANY way Mewtwo does not suck.
Just for your eyes only, Kingler, here's something you should take a glimpse into:
#242 - Blissey
Ability: Natural Cure[Heals status when switched out]
Serene Grace[Promotes added effects]
Base Stats: 255
Sp Att: 75
Sp Def: 135
Trust me, it will make the opponent really happy if you teach Eq to Blissey. And be sure to EV train it if you have "Counter", otherwise it will not survive much.
You are wrong if you think "Recover" is wasted on Mewtwo. With 106 base HP and a Pokemon like him, it definetely pays to have him stay in the game. His most classical set is at the same time lethal: Substitute, Psychic, Calm Mind and Recover. You can change Psychic to something else and he would still be awesome.
One last thing, remeber that all Deoxys have tiny, teeny, weeny, pathetic HP. I am very sorry to state so, but how much of a problem can they all be with so little HP? Wouldn't a Blissey also pawn a Deoxys(not L-G) just like Mewtwo??? In any case, Deoxys is no more dangerous than Mewtwo or any less. Mewtwo has staying power, Deoxys does not. Deoxys may have more Att. or Sp. Att. and Speed, Mewtwo has better defenses. Deoxys has better Deffenses and Mewtwo has more Sp. Att. and Speed.-
These are the archetypes:
Physical Sweeper - A Pokemon designed to use mostly physical attacks to wipe out the opponent as quickly as possible. Usually has high speed, and must have high attack. Physical types: Normal, Flying, Fighting, Rock, Ghost, Steel, Ground, Bug,
Special Sweeper - Same with a Psysical Sweeper, only the Pokemon has high Sp. Att. instead. Special attacks: Fire, Water, Electric, Ice, Grass, Dark, Psychic, Dragon.
Mixed Sweeper - A sweeper that uses attacks from both physical and special types. It's usually not a good idea(EVs section...) to have both physical and special attacks,
but at times, it may become necessary.
Tank - A Pokemon with high defenses, and usually has a recovering move, Leftovers,
and a move that raises one of its defenses. Its purpose is to stall for as much time as possible. Usually, it only has one attack just in case it's the last Pokemon. However, a Hazer can usually defeat one.
Basically, it's a Tank with one of Toxic, Will-o-wisp, or a paralyzing move, usually Thunder Wave. Protect is also usually on a Pokemon with these moves to let the effects take place. Clerics can beat this.
Annoyer - It's made to annoy. It's best used on Pokemon that can take hits since some are chance based and need to be able to survive an attack. Annoying moves example: Confuse Ray, Toxic, Charm etc.
Hazer - A Pokemon with Haze. The faster, the better, but it's not essential. It's used to counter Pokemon such as Gyarados with Dragon Dance. Defense is also preferred in case the opponent already has powered up.
Pseudo Hazer - It's a Pokemon that uses an attack with an effect like Haze and with the purpose of Haze such as Roar and Whirlwind.
Cleric - A Cleric is a Pokemon that is used to heal the status conditions of other Pokemon using moves like Aromatherapy and Heal Bell. Pseudo Passing moves are also usually on them.
Pseudo Passer - Some attacks give boosted defenses or heal, and the effects stay when switched out. These are called Pseudo moves, and are often used to give Pokemon some defense. A Spiker handles these quite well.
Spiker - A Pokemon with "Spikes". Tries to encourage or force switches so the opponent takes a lot of damage. 3 layers of Spikes is the max and most effective amount.
Toxi/Pyro/Parashuffler - First, use your status move, then you shuffle the opponent using an attack like Roar that forces them to switch, so you can inflict the opponent's entire team with an annoying status condition.
STAB - Same Type Attack Boost
HP Type - Hidden Power then what type it is.
Subpuncher - A Pokemon that uses Substitute then Focus Punch. Since the opponent can't deal damage even if the Sub breaks, Focus Punch hits with devastating power.
Baton Passer - A Pokemon that utilizes the "Baton Pass" move. If you have a very fragile Pokemon like Ninjask, then place all EVs into HP and defenses as well as nature, as it is fast enough and has speed boost to BP before it dies. For others, you'd normally want some Speed EVs to take a hit, stat up, then quickly BP. Defenses are good too, but again no attacking stat EVs.
Man, that was tiring. Enjoy...