After talking to my teacher...as mentioned above, the grade requirements reflect the demand.
For example you see courses with low requirements because the University is either a Metropolitan Uni etc.
Ive applied to SOAS for History knowing they have one of the best History Dept in the country. Their requirement is ABB/BBB but ive heard you generally need AAB as a requirement.
Just because the University might have a low requirement doesnt make it a bad Uni. Its just that they want more applicants. For example Govt and Economics i think at LSE want ABB, but with only 50 or so places, people will need AAA/AAB prediction.
I mean when you bring Lg tables into consideration. On the Guardian SOAS is ranked 8th but is around 20th on the times. It just depends. SOAS is a very specialist Uni and their tradition is different to that of other Uni's. I mean some one who wants to do an Asian Language will love it there. 100's of students who have the same interest. Same with History students. But then those who look at languages as "mickey mouse subjects" will obviously have something to say about SOAS