That two hours of studying for every hour of class rule is bogus. Going by one hour of studying for every hour of class is probably a bit more fitting, but that also depends on the class and what you're doing.

For example, in my Finance MBA class, YES, I definitely needed to put in more hours because that stuff can get tricky and I needed to religiously stay on top of it to do well. For marketing, not so much, that doesn't deal so heavily with numbers and formulas. My electives were also a breeze for the most part and I was able to ace those without ripping hair out.