Yes he is.
The concept that Christ, through His Incarnation, is closely united with all creation is hardly an heretical notion.
You may note that nowhere in the above article does Derksen criticize the idea that "Christ, through His Incarnation, is closely united with all creation ," so the fact that it is not a "heretical notion" is not relevant to the current discussion. You are merely arguing with strawmen instead of with the actual substance of the debate.
I need hardly point out that phenomenology began as Husserl's effort to return to Plato. I personally prefer the Thomistic/Aristotelian approach to moderate realism but I cannot pretend, as Derksen does, that the Augustinian/Platonist view is either illegitimate or unfruitful.
You may not wish to argue it, but Derksen makes a very convincing argument that Husserl's phenomenology is "illegitimate or unfruitful." It is false and it is destructive. If you wish to take the opposite position, where is the fruit? Nor is it correct to conflate Plato and St. Augustine as you have done. Augustine was a severe critic of Platonism, especially the neo-Platonism of his day, but Plato himself as well.
One would be more justified in arguing that Derksen's position, which implies that Christ is not united to the world he created, smells of Marcionism, Manichaeanism and Catharism.
If that's the case, then perhaps you ought to argue it instead of simply throwing around innuendos and veiled accusations of heresies.
Derksen is specifically citing a passage in which the Pope argues this position as evidence of the Pope's allegedly heterodox humanism.
This is not a straw man. Derksen is creating a straw man by saying that man is not a legitimate subject of revelation and that therefore statements about man qua man are somehow suspect.
You may not wish to argue it, but Derksen makes a very convincing argument that Husserl's phenomenology is "illegitimate or unfruitful."
There are indeed problems with phenomenology, as there are with Aristotelianism, Platonism, Kantianism and every other purely philosophical system.
If you wish to take the opposite position, where is the fruit?
Husserl's own phenomenology inspired him to accept Christ as God. Husserl's best student was St. Teresa Benedicta of the Cross who converted from atheism to become a Carmelite nun and who died heroically in the Holocaust.
Her writings contain a moving phenomenological investigation of the Incarnation and the meaning of the Cross.
Nor is it correct to conflate Plato and St. Augustine as you have done.
Augustine argued his points using the vocabulary and analytical tools of neoplatonism. One need only read his De trinitate to see how obvious this influence is.
Augustine was a severe critic of Platonism, especially the neo-Platonism of his day, but Plato himself as well.
And St. Thomas did not accept Aristotle uncritically either. Likewise, Pope John Paul II does not uncritically accept everything Husserl thought.
If that's the case, then perhaps you ought to argue it instead of simply throwing around innuendos and veiled accusations of heresies.
Derksen's statement that Christ only came to teach about salvation and deity and not about man is a statement that neither Marcion nor Manichaeus nor the Cathari would have any problem with. Yet it is a deeply disturbing statement for an orthodox Catholic.
That is a concise statement of why his position does not pass the smell test.