If there is an exception to your "always" then your "always" isn't always, is it?
In any case, you haven't explained why in every instance where Paul uses "us" or "we" it must be understood that he is speaking only of himself and those with him. Certainly, in the first chapter of Ephesians, this is not how Paul writes. He is very clearly using "we" and "us" and "our" to refer both to himself and those to whom he is writing.
Ephesians 1:1-6
1 Paul, an apostle of Christ Jesus by the will of God, To the saints who are at Ephesus and who are faithful in Christ Jesus:
Paul makes very plain here who he is addressing and to whom his following words apply.
2 Grace to you and peace from God our Father and the Lord Jesus Christ.
3 Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ,
Since Paul makes no distinction between himself and his audience to this point, it is quite appropriate and reasonable to understand his words as applying equally to himself and to those to whom he is writing. There is no "we" and "you" here in the application of Paul's words, only "us."
4 just as He chose us in Him before the foundation of the world, that we would be holy and blameless before Him. In love
5 He predestined us to adoption as sons through Jesus Christ to Himself, according to the kind intention of His will,
6 to the praise of the glory of His grace, which He freely bestowed on us in the Beloved.
Paul is describing here what is true for himself and his audience. Nothing in what he writes here indicates he is not intending his words to apply to those to whom he is writing. So, we have a pretty glaring exception to your assertion about Paul's use of "us," "we," and "our" in his various letters to the Early Church. Are there others? Yes. Maybe, then, you ought to reassess your certainty and rethink your understanding of Paul's use of pronouns.
There is no exception! The exception is that he didn't identify his 1st person plural from the beginning! He does so in every epistle except Romans and Ephesians.
Do you not think that the person who delivered this letter told them whom all it was from?
The problem is you get to pick and choose whom he's referring to. Please then, why did he say "and you-all also" in Ephesians 1:13? Your as confusing as 2 Corinthians 4:
Therefore, since we(as if it refers to you and I) have this ministry, as we received mercy, we do not lose heart, but we have renounced the things hidden because of shame, not walking in craftiness or adulterating the word of God, but by the manifestation of truth commending ourselves to every man's conscience in the sight of God. And even if our gospel is veiled, it is veiled to those who are perishing, in whose case the god of this world has blinded the minds of the unbelieving so that they might not see the light of the gospel of the glory of Christ, who is the image of God. For we do not preach ourselves but Christ Jesus as Lord, and ourselves as your bond-servants for Jesus' sake. 2 Cor 4:1-5 NASB
If we read 2 Corinthians without giving the personal pronouns their proper reference, then we have misjudged the Corinthian church as being antinomian. Why? They would be right up there with the Philippians, but First and Second Corinthians shows us that they are not at that level of development and therefore, are not a part of the “we”:
Now let’s read it with the correct reference given us in 2 Corinthians 1:1--Paul and Timothy.
Therefore, since we(PT) have this ministry, as we(PT) received mercy, we(PT) do not lose heart, but we(PT) have renounced the things hidden because of shame, not walking in craftiness or adulterating the word of God, but by the manifestation of truth commending ourselves(PT) to every man's conscience in the sight of God. 2 Cor 4:1-2 NASB
Do you see how much it changes the meaning? I always found 2 Corinthians rather difficult to read because it didn’t seem to flow. It keeps going from “we” to “you” which never really made a lot of sense. Frustrated one day, I went backwards to see just who this “we” was. I found it in chapter 1 verse 1, Paul and Timothy--thank God! I then reread the entire book! I was absolutely floored by the intimacy of the relationship Paul and Timothy experienced with the church(called-out-ones) at Corinth. 2 Corinthians is an extremely intimate book which shows us the intimate relationship a pastor has with his flock. And reveals to us why pastor-teachers lives sometimes look so different from our own.
For we(PT) who live are constantly being delivered over to death for Jesus' sake, so that the life of Jesus also may be manifested in our(PT) mortal flesh. So death works in us(PT), but life in you(congregation--that’s a huge difference). But having the same spirit(breath) of faith(noun), according to what is written, "I BELIEVED(trusted), THEREFORE I SPOKE," we(PT) also believe(trust), therefore we(PT) also speak, knowing that He who raised the Lord Jesus will raise us(PT) also with Jesus and will present us(PT) with you(congregation). For all things are for your(congregation) sakes, so that the grace(joyous favor, thriving joy) which is spreading to more and more people may cause the giving of thanks to abound to the glory of God. 2 Cor 4:11-15 NASB
The entire book goes from “we” to “you”. My suggestion is that everyone read 2 Corinthians with the proper personal pronoun references which he never breaks from. It will be like reading 2 Corinthians for the first time. And, you’re welcome.
Now, if you think that somehow Paul changed the way he writes for one book: you are the one making an exception--not me!