I dont consider "height" as a parameter to performance, especially for a batsman. Actually the shorter guys have a lower cente of gravity and thus get into line with the ball much better and are lighter, thus have more nimble, sharper footwork than a taller guy would...Just look at Gavaskar, Langer or Sachin. However, the taller guys generally speaking exude more confidence and as an opener one needs extraordinary self confidence and belief to succeed. So that probably explains why the taller openers are dominating world cricket at the moment.