"philoctetes's final refusal is the refusal of a man so wounded as to be unwilling to resume normal life itself because, with that life, will come new and unpredictable suffering. Better the old known pain, with the old known remedies, than the new hurt as unforeseeable as the future itself ... Only at the cost of suffering does life itself exist."
From David Grene's introduction.
The use of deus ex machina may have been jarring to some but it seemed fitting for me. The world of Sophocles, especially the world as represented in Philoctetes is one where the arbitrary and sometimes incomprehensible words of the gods prevail over human will or toil. Running away from your fate is always futile and leads to further tragedy, until you wield. In such a world, that the conflict between Philoctetes and the world (not just with the Greeks or even Odysseus - this man's grief is rather with humanity and even the entire world, including fate and gods) should be resolved by deus ex machina is natural if not unavoidable.