Well, firstly, does that average include your first year, or is it second year only? Also, I think it depends on the marks gained in exams related to the PhD. For example, if two people both have your average, but one has 75% in a neuroscience module and 50% in a pharmacokinetics modules, and another person has the reverse, the former would be at an advantage with a neuroscience-related PhD. When all's said and done, I would suggest that they're more likely to look at your references than one or two exams scores, especially second year exams. They'll also want to see how you perform in interview.