Example: if you use Thunderbolt for better accuracy, you may fail to OHKO a threat that Thunder may finish off. If Thunder misses then it is still a 2HKO (considering the next attack hits), meaning the trade off for TB will be of no loss; if it doesn't miss however, you reap greater benefits for better taking a bigger risk. You control the numbers that you're willing to play with and go with it; manipulating these numbers in your favor is a large part of skill in Pokémon. Evasion reduces this effect, lowering the probability of a payoff on either end, taking "management" away from you and giving it to the RNG. Is this, a greater precense of luck, something that we want in the metagame?
Doesnt Evasion increase this effect? For instance now you have a choice between Thunderbolting a pokemon which will 2hko; or you can Thunder which will OHKO protecting you from a hit, but increasing the risk; or you can DT first and then Thunderbolt or Thunder, which has the most risk, but potentially the greatest payoff. This only adds to the management.
If you are facing an Evading pokemon you still should consider the benefits of Thundering and OHKOing or Thunderbolting and increasing the likelihood of 2HKOing.
Double Team / Toxic / Protect / Softboiled.
This set is awful. It is countered by Rest, Substitute, Steels, Poisons, Toxic. Any physical attacker with a decent Fighting move still has a 1/3 chance of OHKOing you once you are fully DTed.. Even with Flamethrower over Protect, it still isnt likely to really reap the benefits of DT.
Basically, DT here is protecting you from pokemon that 2hko you (pokes that dont 2hko you arent going to be able to finish you off while you have softboiled). Which DT is very unlikely to achieve. With a DT, a poke still has a 56.25% chance of hitting you twice without missing. IE more often than not, DT will do nothing on this set.
The reason the strategy is banned and will be banned forever (even if testing does take place understanding the mentality of the community leads me to believe if would never be allowed in standard play) is because this community despises "luck based strategies". While evasion moves may not make a difference in the larger perspective, individual games would be lost based on evasion moves and I assure the community does and always will find this despicable.
The community is following a status quo established in RBY when Double Team really was the best move. But please dont speak for the community, speak for yourself.
I recently faced a SubGliscor in the Sand holding Brightpowder was haxed out of a win (the player wasn't even decent). If Double Team was somewhere on that moveset, I would of seriously told the player to fuck off out of frustration.
This sounds a lot more like a prejudice than an actual argument. You lost anyway - obviously you couldnt hit him when you needed to, so what difference would DT have made? It would have meant he would have had one less other attack, so maybe it would have allowed you to stall him out or something.
The Shuckle you faced, I am sorry, but that is a terrible moveset. See my description of the Blissey above. That Shuckle is actually worse..
Imagine if somebody used something like Gliscor with Sand Veil, DT, Bright Powder, Substitute, Roost and Baton Pass to setup something like Lucario or DDtar? This would probably fall under the Support characteristic of Tangerine's definition of an Uber with a little bit of testing.
Would you be willing to ban Gliscor to make Double Team legal?
That Gliscor is easily countered by Roar. You DT I send my Roarer, you Sub I Roar, I have a 54% chance of hitting you. You BP I have a 75% chance of hitting you. Meaning a 11.5% chance you will successfully pass 1 DT and a Substitute. What if I then send out Gliscor to counter your Lucario. I have a 75% chance of hitting you, but you only have an 80% chance of hitting me. And again, more often than not that Gliscor will 2HKO you without missing once.
Have a nice day.