Sandman was published by DC. As for political content, you'd be hard-pressed to find a much more left-leaning publication than Hellblazer. Granted, DC isn't continuing either now.
Also relevant.
Hellblazer, what a great comic that was. Loved the Garth Ennis run on it and you can see where he got the idea for Preacher. I was collecting both Sandman and Hellblazer at the same time when they came out.
DC really pushed the envelope covering a wide range of topics in their super hero titles (domestic violence, sexual orientation, gun violence, homelessness, racism, AIDS) before the Vertigo label came out. I know Marvel did similar but to say DC was conservative back then is a bit head scratching for me. Even Hellblazer and Sandman were released in the late 80s. DC allowed writers to take their characters into so many directions.
Also, good link. Explains why I like DC Comics more than Marvel. When I look at the example in the link, I'd choose Kamandi because it comes across as a more interesting story and setting which is what I prefer.