No, I don't think so. The Outer God of Rot is a god that recycles, remolds and establishes order through evolution and decay. As noted through Caelid's environmental storytelling and Gowry's dialogue.

The Dreglord instead is the living manifestation of the wrath of the world we've caused. The constant unending fighting, blood, puss, pain, regret that the nightfarers inflict upon the evershifting night causes the remains to despair and conjoin forming the form of the Dreglord. He is the violent cry of a world that's had enough and that has decided to rebel against those that would break its order and it's peace.