1. personal ability is always the most important, but normally are not within consideration while university/program selection - it is likely a constant factor given in advance...
2. Overall ranking, well, I should say overall university reputation, is useful for job seeking indeed - mostly for passing CV screening. But we all know that putting UCL at 7th is indeed the joke of UCL as no one really believe that seriously.
3. MSc is useful for academics purpose too. Most of the universities outside US need a master for application of PhD.