well i think memorising is actually a good thing to do for economics because there are only a certain amount of questions they can ask you......its not like business studies where the range of extended response questions is virtually endless.....
the syllabus pretty much outlines the different questions that can be asked, so if you were willing to put in the time to write a near perfect essay then memorise it for each different essay, you would definitely be fine......the only thing is that they can change the verb in the essay questions e.g. from evaluate to analyse, and if you dont take that into account then it could lose you a few marks....
on the other hand, i just wrote practice essays for most of the topics and memorised the structure i would use for broad essay questions that could come up, then as i was writing, i would eliminate the paragraphs/points that weren't applicable to that particular question...... i suppose that this is a pretty obvious/logical method, but the difficult thing is actually doing it. it is best to make the essay scaffolds as you go rather than just when the exams come around - makes it much easier to study