I think largely they are fairly accurate but they do need to be looked at carefully. There is no great difference between 10 and 20 so they should just be looked at for advice. However I think they are useful to say if a university is a better university. For example a top 20 university will usually be better than bottom 20.
As far as York is concerned it used to be far higher and dropped down for some reason so I an not surprised it has climbed again.
One of the problems with tables is they use student satisfaction rates and these really fluctuate. The student satisfaction rates in London in particular tend be very low and higher ranked universities sometimes suffer as the higher graded students tend to have higher satisfaction levels.
As far as the Russell Group universities are concerned I think the problem is that students are led to believe they are the only good universities and this isnt true. As the list shows St Andrews, Lancaster, Bath and Loughborough are all non RG universities and all top 10 in the rankings. Just because a university is in the RG doesnt mean it is automatically better than one outside. Royal Holloway and East Anglia rank higher than Liverpool and Queen Mary. One of the things I have never understood about the RG is why Bath, St Andrews and Lancaster weren't admitted when Queen Mary was along with Durham, Exeter and York back in 2011.