Well, the only team of mine that did anywhere close to decent was comprised of the three legendary dogs with their standard level 40 movesets. (Mind you, this was before I knew anything about competitive battling, so they weren't even EV trained.)
I think I got within one or two matches of completing the challenge a few times, but I never actually beat it. From what I've heard, though, even a well-built team doesn't stand a chance against the cheating computer.