It is only the modern liberal and ephemeral mentality that makes the works of great philosophers 'obsolete'. Learned opinion suggests otherwise;
"Heidegger's work has influenced such varied fields as theology, existentialism, contemporary hermeneutics, and literary theory and deconstruction".
[T.Mautner, Dictionary of Philosophy 1997]
Heidegger's four volume 'Nietzsche' still stands as one of the great interpretations of that philosopher.

To object that this magnum opus was 'more about Heidegger than Nietzsche' shows a complete ignorance of Nietzschean philosophy. Nietzsche's own essay 'Schopenhauer as Educator' was later regarded by NIETZSCHE HIMSELF as all about Nietzsche and not Schopenhauer! So much so, that;
"One can replace the name Schopenhauer with 'Nietzsche' throughout the essay".
[Nietzsche 'Ecce Homo' on Schopenhauer as Educator]

The whole philosophy of perspectivism makes this NECESSARY!
Just as Schopenhauer revalued Kant, so did Nietzsche revalue Schopenhauer, and Heidegger revalue Nietzsche. All great philosophers learn from their own intellectual predecessors and then transform that learning into something OF THEIR OWN! - that is not 'distortion'.

Heidegger has this to say of Dionysos in his 'Nietzsche';

"What the words 'Dionysos' and 'Dionysian' mean to Nietzsche will be heard and understood only if the 'Eternal Recurrence of the Same' is thought.
In turn, that which eternally recurs as the same and in such wise IS, that is, perpetually presences, has the ontological constitution of 'will to power'.
The mythic name 'Dionysos' will become an epithet that has been THOUGHT THROUGH in the sense intended by Nietzsche the thinker only when we try to think the COHERENCE of 'Will to Power', and 'Eternal Recurrence of the Same'; and that means, only when we seek those determinations of Being which from the outset of Greek thought guide all thinking about being as such and as a whole".
[Heidegger, 'Nietzsche' Vol II, sec. 26]