I would agree. Of the three, I think probably Ligotti and Howard have the darkest outlook. My impression of Lovecraft, especially in reading his letters, is that he had a detachment from his intellectual vision, being able to overcome some of his anxiety and actually enjoy being alive as a civilized gentleman and artist. I don't know how much of Robert E. Howard's writings Ligotti has read, but he is at least philosophical heir to Lovecraft; and Howard in his turn was inspired by Lovecraft, so they are all connected.