The ratings depend on the mood of the guy assigned to put them together. The whole defense got a 6 but I've seen worse defeats by a team where the rating are not applied in that fashion. For example, St. Pauli with Gibbs lost 4-0 and I think the ratings were better distributed.
Generally I agree with about 95% of the kicker ratings. In this case I don't. I already told them that this is kind of fan behaviour to sit down after the game, have some amounts of beer after the disappointment and claim that the whole defence was crap. Of an expert magazine I expect that they are doing a detailed analysis and don't do any blind generalising as they did here. But the ratings also do not depend on the result of the game. Bochum had 14 chances to score - that's usually what you get against a team two divisions lower. This indicates a crap defence and also that some of the ratings might be right.