I think I'm more disappointed that they don't have the license to air Durarara!! than I am with losing the license to Deadman Wonderland and Casshern Sins. Deadman Wonderland was surprisingly entertaining, along the lines of a popcorn movie, but not something I'd want to see again. Casshern Sins was more interesting and it really improved in the second half, but I don't know if I'd want it on the block again. Although, even without the license issue, I couldn't see them airing Casshern Sins again given the ratings it normally got. Durarara!! would have fit on the block pretty well and maybe it could have worked during Brotherhood's slots. It would have been nice to see the series again.
I imagine that this would probably connect to their small budget and airing the series once would save them from spending more money to keep them around for another run. Personally, while I'm disappointed that they don't have Durarara!! available, it's probably for the best since they can try to get new and hopefully better shows, which is what the block really needs. Although, given the first impression I got of GXP, I'm thinking that they were running really low for a new show and just went with a really cheap one that they could afford.