These "random" requests look almost exactly the DGA for Murofet- a Zeus variant. This has caused some problems for us (and other vendors, I would assume) in the form of massive numbers of false positives. In short, it's been kind of a PITA.
I wish they wouldn't do this, but it is definitely a tough problem to solve and I can't think of a better approach off of the top of my head. The ultimate culprit is the ISPs that return an A record for a DNS request that really should return NXDOMAIN. These ISPs are essentially breaking the Internet, and we're all just scrambling to put band-aids in place to get it to work again.