I will agree with the last point-- you put what I was going to allude to into words just now, though I was trying to work out the whole "energy requirement thing". However, my reasoning for agreeing with this goes towards my retort.
My retort to the argument that being 2-C is a rational stopping point for questioning for evidence goes as follows;
First off, having 2-C durability doesn't necessarily mean that you have anything beyond impossibly tough physical durability. I'm under the impression that all we do when we adopt the concept of universal+ durability (or multi-Universal, whatever 2-C we're talking about) is that this character is capable of resisting an impact or any generated energy with enough Force behind it that it could destroy a Space-Time continuum (if I am mistaken, correct me if I'm wrong). We operate under the hypothetical idea that there is some incredible amount of power/force/energy that is capable of destroying Space-time through raw power-- it would be through hax if done otherwise (right?). I liken this to The Flash and him breaking the "Time Barrier"-- the writer operates on a similar hypothetical assumption to ours, where there is a speed you can reach that "breaks time" or some shit. The point is, I figure that, since being 2-C in durability is supposed to mean that you can resist a powerful force that can bust a Space-Time of a Universe or multi-Universal tier stuff, and if this is the case, then when it comes to hax that produce change in physical objects (like transmutation) or, even more so, when hax comes in contact with another character's energy (like tier 9-A Soul Manipulation on a DBS level Chi Manipulator), the question becomes "Does the Hax user have enough energy to affect the Target?"
An example.
Soul hax from a 10-C vs a 2-C with Chi Manipulation and Universe+ levels of power in AP and some kind of Energy enhanced or "Spiritual Energy Durability" or something. Basically ask yourself if Soi Fon could instant kill Beerus-- who has some form of Spiritual Energy that is on a completely different tier from her that is capable of Universe busting shit-- when Soi Fon has to use her Spiritual Energies to not only activate and use the attack, but to make the attack produce change in someone as powerful as Beerus, who has far more raw power/energy than she does. Energy is also known as the ability to do work. Are you telling me that, if Beerus was 3-A or even just planet level, Soi Fon can use Suzumebachi to produce change in the Spiritual Energy of someone who has far more capability to "do work" than she does? It's like asking a Transmuter who can turn a house into a rock to do that with a planet, like Pegasus said. A better example is with Itachi vs Buu. Assuming Buu doesn't blitz or anything, since Genjutsu is done by Manipulating your opponent's Chakra/Ki/Spirit Energy into affecting their biology and therefore their senses, can you really say that Itachi can manipulate Buu's Solar System busting Energy???
If I'm wrong about what durability on a 2-C level is, then allow me to ask questions.
1. Are characters like Jiren and UI Goku 4th Dimensional? That doesn't really make a lot of sense if this is true, because physically, they should be 3-D beings. And it doesn't sound logical to be both Bound By Time as a 3-D being and be beyond/a part of time/able to move through time like space as a 4-D being. If being 2-C means also being able to exist beyond time and stuff, along with other higher dimensional perks, then shouldn't that just add to their list of power-- shouldn't that mean that all 2-C characters get powers they hadn't displayed or shown by nature of being able to survive Universe+ levels of force and that's it?
The point to 1 is that being 2-C in durability should be seen as nothing more than any other durability level, as all other higher dimensional aspects associated with being 2-C aren't inherently attached to being 2-C, by my understanding.
2. We have characters who are able to use abilities that have nothing to do with raw power and have their attack potency be extremely high. For example, Naruto and Sasuke are listed as Moon Level in AP, when the moon was hollow and they can only do stuff on Moon Level with Chibaku Tensei, blah blah blah, yet their AP is listed as Moon Level, as well as other characters having a similar issue where their AP scales to whatever they did without using an actual blast, yet we assume that they're able to channel that power from the ability they used into an energy attack.
The butchered point in #2 that I'm trying to make is essentially, energy is required to do things-- including produce change, affect, alter, destroy, whatever it might be. I think this concept should apply to all hax, physical, and metaphysical. Think of the metaphysical part being able to overcome or alter energy like wrestling, lifting, or altering something. It requires energy for a chemical reaction to take place (I would liken a lot of hax to chemical reactions, producing change in a rather indirect way). Same concept for hax. If you don't have the capability of producing change on the level capable of affecting a tier 3, then you probably shouldn't be able to hax them-- depending on the type of hax and their type of power. Haxing tier 2 Frisk's soul as a 8-C doesn't really seem thesible, even if you bypassed similar defenses to those Frisk put up. Frisk/Chara should be far too powerful to affect from that level-- like a baby bending steel.
Don't @ me about any changes to profiles, I just bring these facts up to say that, because energy is defined as "to do work", it would only make sense that a character requires a certain amount of energy to produce change in another character-- and if that character is able to resist and or put out the same kind of energy being used-- then their had shouldn't work because they don't have the energy necessary to affect these kinds of beings. Not all hax works independent of durability. I would argue most of it might not. Mind Manipulation requires biological stimulation in many verses, Soul and Spiritual Energy based hax might be combatable if the other user has Superior versions of either or.
Objections?