Did you do the essays before going to Quant and Verbal sections on each of your practice tests, including GMATPrep?
It is obvious that Verbal is your weakness, and you need to quickly analyze which part of Verbal you need to spend your time more. If possible, arrange the SC, CR and RC in an order that represent the strongest to the weakest area, then start with the weakest one. I have a feeling that you have mastered all the concepts and strategy on different types of Verbal questions. Thus, it is just a matter of practice. I have always emphasized that test takers only use OG and GMATPrep to practice their skills since both contain questions that most resemble the ones you will see on your real test. On the other hand, you don't want to overuse both materials as you won't gain anything from doing so.
I'm not sure how you approach each Verbal question, but I learned from a GMAT tutor that for each Verbal question you encounter, not only you must be able to identify the correct answer, but also it is equally important that you know why the other answer choices are incorrect.
Very often I looked at a question and after scanning the answer choices, was able to quickly pick D, for instance, as the correct answer. But then, after scrutinizing answer choices A,B,C and E, I can eliminate A,C and E for sure, but not B. After looking closer at both B and D, it was not unusual that I switched my answer to B, and indeed, B is the correct answer.
My point is, for every OG and GMATPrep question you tackle, knowing why incorrect answers are incorrect is almost as important as picking the right answer. If you haven't done so, I suggest that you do your practice on OG and GMATPrep but with different approach.
I hope this helps...