Last boss. Of course it is. Why would it drop anywhere but the hardest place to get it? -_-
Isn't Hazmat (which I believe is the same thing as Dread Guard except without set bonus) able to drop anywhere throughout the op though? I don't care much about the name or the set bonus, just the look.
the only boss that drops hazmat anything, is the buckteeth gopher (first boss), everyone else drops set piece tokens.