Fr Dreher is mistaken.
Since you're well armed with articles and the history of the practice, I assume you've read Fr John Dreher's 1997 article objecting to the practice called
The Dangers of Centering Prayer? He goes into the background of the Trappist monastery where the practice originated, noting that they hosted speakers and retreat leaders from various eastern faiths quite often which seemed to have a strong influence the way it did over Thomas Merton.
I find I agree with Fr Dreher if for no other reason than to err on the side of caution.
From the article:
"My hypothesis is that it is Satan’s strategy, in all these things, to strip away the physiological and psychological forces that, in our fallen state, are a fail safe protection for the human spirit. (This is a possible interpretation of Paul’s words in 2 Thessalonians 2:6–10 about the lawless one and the force that restrains him.) Thus, he can hope to capture the spirit of man worldwide and establish a kingdom of darkness."
The author's basic hypothesis is wrong. He assumes the our fallen physiological and psychological forces restrain Satan. How silly. Common sense and St John of the Cross, a doctor of the Church, tell us that rather than restraining Satan they are the materials through which he tempts and distorts us. That is why St John speaks of :
1. THE second positive evil that may come to the soul by means of the knowledge of the memory proceeds from the devil, who by this means obtains great influence over it. For he can continually bring it new forms, kinds of knowledge and reflections, by means whereof he can taint the soul with pride, avarice, wrath, envy, etc., and cause it unjust hatred, or vain love, and deceive it in many ways. And besides this, he is wont to leave impressions,496 and to implant them in the fancy, in such wise that those that are false appear true, and those that are true, false,
And finally all the worst deceptions which are caused by the devil, and the evils that he brings to the soul, enter by way of knowledge and reflections of the memory,
Thus if the memory enter into darkness with respect to them all, and be annihilated in its oblivion to them, it shuts the door altogether upon this evil which proceeds from the devil, and frees itself from all these things, which is a great blessing. For the devil has no power over the soul unless it be through the operations of its faculties, principally by means of knowledge, whereupon depend almost all the other operations of the other faculties.
Wherefore, if the memory be annihilated with respect to them, the devil can do naught; for he finds no foothold, and without a foothold he is powerless.
2. I would that spiritual persons might clearly see how many kinds of harm are wrought by evil spirits in their souls by means of the memory, when they devote themselves frequently to making use of it, and how many kinds of sadness and affliction and vain and evil joys they have, both with respect to their thoughts about God, and also with respect to the things of the world; and how many impurities are left rooted in their spirits; and likewise how greatly they are distracted from the highest recollection, which consists in the fixing of the whole soul, according to its faculties, upon the one incomprehensible Good, and in withdrawing it from all things that can be apprehended, since these are not incomprehensible Good. This is a great good (although less good results from this emptiness than from the soul's fixing itself upon God), simply because it is the cause whereby the soul frees itself from any griefs and afflictions and sorrows, over and above the imperfections and sins from which it is freed.
Ascent of Mt Carmel
Book Three Chapter 4 p. 194-5