It's no surprise to see the two so-called 'massive' clubs topping the averages, but there are mitigating circumstances. Leeds play around half their away games within an 80 mile radius (11) and Wednesday aren't far behind (9) which makes travelling cheaper and more convenient.
Compare that with Brighton (only 4 and all over 50 miles away) and Boro (just the 1 and 72 miles away) and it can be argued that proportionally these two clubs have more of a fanatical hardcore away support than the 'sleeping giants'.