@Saikou Let's calm down a little here. This isn't anything to get worked up about.
First of all, this situation isn't a viable use of
powerscaling. We cannot scale the Wither to the Ender Dragon.
Note the following examples.
"Character A is City level, and Character B was able to survive attacks from or harm Character A. However Character A was holding back, restricting themselves, not putting their all into their attacks or was in a weakened state during the fight, then it is not safe to assess that Character B has City level AP or durability. As this would clearly indicate that the two do not have comparable power and that one is much superior to the other."
The Ender Dragon is in a weakened state during this fight, and can't use its End Crystals to regenerate, which would otherwise make this a stalemate. The Ender Dragon also doesn't put its all into its attacks, as it doesn't actively pursue the Wither during this fight; rather, the opposite is true: the Wither pursues the Ender Dragon while it flies around aimlessly. If the Ender Dragon actively and continually attacked the Wither, it would be a stomp in the Ender Dragon's favor.
Let's also review some viable uses of powerscaling and why this doesn't apply.
"Character A performed a feat of destroying a City and has City level durability. Character B has overpowered, critically injured and is portrayed as physically superior to Character A. In this case, it is safe to assess that Character B has City level Attack Potency, despite not having feat of City destroying themselves."
The Wither cannot overpower the Ender Dragon. It cannot critically injure it without the End Crystals not being active, and even this is small chip damage accumulated over time from 9-A attacks (which is explicitly debunked in the
Game Mechanics page). It is not portrayed as physically superior to the Ender Dragon.
"Character A has a FTL speed feat, and Character B outpaces or
speed blitzes Character A, then it is safe to assess that Character B has FTL speed as well."
Inapplicable to our situation for two reasons. The first: we're discussing AP and tiering, not speed. The second is that
we also have speed values for every living entity in Minecraft, and the Ender Dragon outpaces the Wither (Wither flies at about 28.5 m/s, Ender Dragon flies at about 30.1 m/s.).
"Character A has a City level feat. Character B lost to Character A, yet still put up a considerable fight, was able to harm him and clearly made Character A exert effort into defeating Character B, then it is safe to assess that Character B has City level Attack Potency and Durability as well."
Inapplicable to our situation, as we want to see if we can scale the Wither to the Ender Dragon (no), not the Ender Dragon to the Wither.
"If Character A has a City level feat and Character B has been reliably stated to be superior to Character A, it is safe to assess that Character B is City level as well."
The Wither has not been reliably stated to be superior to the Ender Dragon.
You state that mobs don't instantly die from the Dragon. However, as stated previously in this thread, several do. Of note are silverfish, which we scale all of our low-tiers to (Regardless, I don't think this is a good idea, if you'd like to see why, go in
this thread and talk there). You mention they can harm things that can survive the dragon, but keep in mind that the dragon is not concentrating all of its power on a singular mob, and not putting its all into that attack. This was discussed in the first example, and is not a valid use of powerscaling.
Scaling fodder mobs to an endgame player because they can slightly damage them isn't a valid use of powerscaling since fodder mobs cannot possibly put up a considerable fight one-on-one.
I am not "pretending that the Ender Dragon is
infinitely above
everything else in the verse." Don't strawman my argument. I've provided an amount in Joules for its most powerful feat. It's not headcanon, it's a simple calculation.