How to WP_Query() from multiple blogs and order them?

Dear WordPress community,

my job seems quiet hard now. We have a blog for articles and another for videos and I now have to produce a list of it, ordered. Paginatedly. This is what I tried:

and:

the problem is, the output is not correct of course. Both the resultset can only be appended not merged. The best would be:

but as of my knowledge, its not possible. Then how?