To be honest, I found Diablo 3 to be a bit mediocre. That's an opinion. I respect that loads of people love the game, it's just not for me. Rock Paper Shotgun can have an opinion contrary to the mainstream one. The site is a blog, not an online magazine, so it is just opinions.
They aren't trolling for traffic, they don't need to, they're bigger than Giant Bomb last time I checked, and the argument that they're trolling for traffic is just as bankrupt as the idea that Giant Bomb are trolling for traffic when they didn't give Skyward Sword the full 5 stars.