I'm also on Tumblr under SchwarzerAlptraum (beware; I have a bunch of horror NSFW stuff there as well). I guess that is what I like about Tumblr over DA. You get some freedom in the content of your postings, but I'm not really fond of the layout. It's got too much ads, and there are some people I like to watch because they have good art, but then they proceed to bombard their Tumblr blogs with other irrelevant stuff I'm not interested in, and I don't have that much time to trawl through everyone's posts on my dashboard. I guess it's a bit hard to cater ads on Tumblr that is actually relevant because Tumblr doesn't exactly have a theme or a target audience in mind. It's a lot easier to do stuff like sponsor or host ads for artists on an art gallery and it won't seem irrelevant, annoying or dangerous.

Because of its format though, I tend to treat Tumblr like a free for all blog where you put all your scraps. I don't usually post scraps on my other art galleries. I reserve Tumblr for that.

It might not actually be such a bad idea to have a Paperdemon account on Tumblr. You can post updates and other dev related things, or just stuff in general. I know other art platforms that do it. It's also a good way to get connected because people know about Tumblr. Of course, that also does take some effort as you still have to follow the right people on Tumblr and get some people to follow you as well.