journey-on,
I'm glad you started this thread. The points you are making I have often tried to make, probably in too obscure a way.
I believe our "separate self," "individual ego," call it as you like, to be a "fiction of the mind," basically a construct of language. But a very necessary one in the general (language-based) structure of mankind. To quote again from Lacan's French formula, les non-dupes errent ("the non-dupe err") -- homonymous in French to les noms du Père, "the names of the Father," by which Lacan pointed to the necessary "Other" referent of the linguistic-symbolic "contract" which makes us what we are. More simply put, without a dose of self-delusion we cannot be "selves" and function socially as such.
"Mystical extasis," in the sense of stepping out of this artificial self, is both an impossibility (in the literal sense of self-delusion) and an evidence (inasmuch as the self itself is self-delusion). I regard it, as I have often said, as a pharmakon -- both a remedy and a poison. Vital to those who need it when they do need it, deadly to those who don't need it.
Let me describe human life with all its social, economical, political, ideological, emotional aspects as a game. If you (as a "separate self," fictional as this is) are neither interested in winning nor afraid of losing, because you always think (and rightly so!) that "it's just a game," you will soon get bored and ruin the fun of it for yourself and others. Otoh, if you are paralysed with fear of losing, or if your desire to win otherwise spoils the game, you will need to be reminded that "it's just a game". But don't jump to the conclusion that every player, always, needs the same reminder.
As many have found, there is a hidden "exit door" in the depth of anxiety, and hopefully anyone who gets there will find it. At this point the testimonies of those who have found it before may be useful. But it is neither something to be proud of nor something to preach to those who are simply enjoying the game, successfully coping with their desire and fears, without feeling the need to question their "self". Not anymore than you would want to share your remedy, no matter how helpful it was to you, to people who are not sick as you were/are (or convince them that they are necessarily sick as you are/were and just don't realise it).
Perhaps this will upset many, but I think Paul's illustration of the body and members offers one of the best perspectives on this issue. In Pauline terms we are "in Christ" (more and less than our individual selves) but at the same time we are different, with separate functions, roles and destinies, the difference of which is useful to all. "Mystical witnesses" are helpful to the body (and, maybe, to any of its members potentially) provided they do not insist that everyone becomes like them.