Even though there is a "Show/Hide Patterns" slide, it seem that most of the questions are clustered together when they share patterns within a difficulty.

Even though I try not to pay attention to the revealed patterns of the near by questions, I often see them. This gives me a very good hint on how to approach to a problem which I won't have when I will be in an interview.

A shuffle button/slide (some might want to get the original ordering back) would solve that problem since I wouldn't be able to guess the pattern with the ordering randomized.