Critics have also stated that the computer-adaptive method of placing more weight on the first several questions is biased against test takers who typically perform poorly at the beginning of a test due to stress or confusion before becoming more comfortable as the exam continues.  On the other hand, standard fixed-form tests could equally be said to be "biased" against students with less testing stamina since they would need to be approximately twice the length of an equivalent computer adaptive test to obtain a similar level of precision. 
Most of us will have to write an essay under a tight time constraint at some point. But just because you write your essay quickly doesn't mean it can't be great. Remember, don't let that panicky feeling distract you. Be sure to read and reread the question carefully and ensure that you understand it before you start writing. Remember to quickly outline the major points that you want to make; this will help keep you on track. Then, write your introductory and concluding paragraphs last, after your body paragraphs, in order to make them apply better to what you've written. And finally, give yourself a bit of time to edit for grammar and content. If you've followed all the other steps, you shouldn't have too many content problems you'll have to fix.