Endless Battle Clause should stay in Anything Goes. exist a difference between Endless Battle Clause and other uncompetitive clauses.
Imagine if the OU tier doesn't have the Evasion Clause nor the more recent Baton pass complex clause .
First of all, every team that uses Evasion as a strategy wants to win the match by making the opponent's moves miss against them.
Second, not every Pokemon is viable with Double Team. For example, Greninja si unviable with Double Team because it's so frail. Also, many pokemon don't have place for a boosting move that only allows a 25% chance of missing an attack and they will prefer (specially by good players) more realiable moves to wins.
Actuaslly there are three types of cases (in my head) where Evasion could be a terror.
Case 1:
Baton Pass teams. The worst of the cases, because they only will have Evasion boosts, but also they'll have boosts in defensive stats, making the chance of miss actually higher
Set example:
Scolipede @ Mental Herb
EV: 248/252 HP, 252 Spe, 4/8 SpD
Ability: Speed Boost Nature: Jolly
-Double Team
-Iron Defense
-Protect
-Baton Pass
alongside things like
Sylveon
Leftovers
EV: 252 HP, 252 Def, 4 SpA
Ability: Pixilate (if Hyper Voice)/Cute Charm
-Calm Mind
-Double Team
-Hyper Voice/Stored Power
-Wish/Stored Power
Case 2: Already strong Pokemon that are bulky that could have evasion moves. One of the most hated possible cases would be:
Garchomp @Leftovers/Yache Berry
EV: 4 HP; 252 Atk, 252 Spe
Ability: sand veil Nature: Jolly/Adamant
-Double team
-Substitute/Swords Dance
-Outrage/Dragon Claw
-Earthquake
Case 3: Bulky Pokemon with the move Minimize. Minimize not only allows to boost evasion, but starting in Gen V it boosts evasion by 2 stages.
Clefable @ Leftovers
EV: 252 HP 252 SpA 4 Spe
Ability: Unaware (ja)/Magic Guard Nature: Modest
-Calm Mind
-Minimize
-Moonblast
-Flamethrower
Evasion is a legitimate clause that has a clear intention of winning the game by making the opponent miss often. Teams that use EVasion has to add more usual legal OU startegies (or a full BP chain) to realistically win a match (even though it depends on the RNG).
Not only that, but Evasion has it's check and counters.
-Haze, Roar, Whirlwind. Moves that delete allt he evasion boosts (both by the EVasion booster switching out or by delelting all the boosts). Those moves never miss in Gen VI.
-Moves that have 101% accuracy (never miss even with Double Team boosts). Those moves are Disarming Voice (40 BP), Aerial Ace, Shock Wave, Faint Attack, Swift, Magnet Bomb, Magical Leaf Vital Throw (70 BP), Aura Sphere (80 BP). If no listed BP, all fo these moves have 60 BP even though the moves are weak, they are stronger than priority moves (usually 40 BP)
Taunt (better if faster). Even though the moves can miss, if the user hasn't ended the Double Team spam yet they were unable to use Double Team more.
-Sheer Power. 75/60% of being hit and being OHKO'ed by a streong move is a serious matter that forces the double Team user to switch.
-Hazards. Hazards ignores Evasion boosts.
-Poison-types using Toxic. Evades Evasion boosts.
In general, if Evasion was legal in OU, the metagame would be more defensive that is right now. almost everything will use near 100% accuracy moves (no more Fire Blast or Hydro Pump), never-miss moves will be a necessity on the team like priority is now (and because the bulkier metagame, it can outclass priority itself)*.
Many of the standard startegies in the OU metagame will still work if EVasion is allowed. The difference is that they will miss more often.
Unlike Evasion Clause, Endless Battle Clause's strategy is to not win the game at all and isrupt a battle completely forcing either user to forfeit which is not fun at all. Users of sets like this:
Slowbro (the infamous Funbro) @ Leppa Berry
EV: 252 HP 252 SpD
-Slack Off
-Recycle
-Block
-Heal Pulse
don't have actual intention of winning. If the user can't 2HKO the Slowbro is very likely that the opponent will have to forfeit, which is not fun at game. Also, this strategy will don't have a solution apart of the competence of the Funbro users, unlike Evasion