I never implied that was the case, Myriad. I even mentioned that IN my comment. Also, blades and sharp objects are not based on the idea of negating durability. Goku says hi, he stops a sword with his finger. Durability is your resistance to damage, in real life, knives and nearly everything bypass our durability in the sense that they hurt us and can cause damage. Negating durability is something else altogether, all the blades do is bypass it. That notion is flawed. Blades have an "AP", so they do X amount of damage. If I have Y durability and Y>X. I resist that damage, Im not affected. Thats the basis on how AP and Durability relate. Negating Durability is, for instance, when you have an attack that works in EVERYONE except those with defences on that, such as Mind Control, for instance.
Once again, I never implied this was the case. I in fat even said this. "Bepo, this may sound weird, but having planet busting capabilities and power doesnt mean you can neccesarily planet bust [...] though I doubt this is the case. "
Even though your durability negation argument is wrong, you can check why that is on threads debating about Attack Potency, Durability and such, you did do so some good points in relation to how it translates into Warcraft. In which case, once again, this is completely irrelevant to the case since this isn't my main argument on an argument at all, I just brought it up to give an example on the fact that there are exceptions to the rules and that there is need to be careful on these.
Now, if anyone wishes to criticize me on my arguments about Arthas, Archimonde and Deathwing, such as Bepo who is quite probably going to instacomment its not proof that they are 5-B and Im gonna have to work a bit harder (Thank you for that, actually), I'd be glad.
EDIT: And to answer your question, Arda, its wrirten on the WoT. Even though they have never outright fought or been compared in-universe (except for Archimonde and Kil'Jaeden, of course), they're feats are quite similar in a greater scale and they are comparable on that.
EDIT2: Deathwing crossing dimensions didn't do 5-B damage, indeed. But that wasn't his power alone. That was the result of his power, similar to one powering up and destroying nearby mountains. Imagine you are under a table. And you rise up so hard you crash the table into two and bypass it. Thats what Deathwing did to reality. I don't know if this can be calculated, but it still needs immense amounts of power to pull off. And Deathwing has faced the Dragon Aspects alone at 10 times the power he currently is, so AP feats aren't really a problem. One could even just say he is superior to Arthas and get done with it.