I agree. The verbal section for the actual GMAT is much harder than any practice test. Though I do believe that MGMAT comes close in verbal in light of my test experience.
Here's a tip for CR, try doing past LSAT Practice tests. LSAT CR is similar to GMAT, but I find that they're thicker and generally harder. I finish GMAT CR questions now at about 2 minutes or less with an 80% hit rate as a result of LSAT CR practice which would be about 40 CR questions a day. Where you find LSAT practice tests is up to you.
I agree, the OG is way simpler than the actual GMAT. It seems like most of the OG math questions are at about 300-500 level MAX. But what's important are the concepts you learn from them. Some suggestions. Search online for combinatorics/permutations tutorials. If you're lucky you can also find some question banks with answer explanations. (On my test day, I encountered at least 4 probability) Don't know if you acquainted with this site,
http://www.beatthegmat.com, but it has lots of resources and great contributors to help you on your GMAT journey.
Personally, I always go back to the inaction problem sets in MGMAT's quant guides. These questions test the theory so well that every time I review it, I get refreshed and my theory solidified. I rarely tackle OG. I went through OG at the beginning of my prep not acquainted with a lot of the strategies. I do refer to the MGMAT additional question banks. If you haven't activated them yet DO IT! There are some tough questions there that really test your knowledge and application of theories. Also, the flash cards are great resource for extra questions and helps you remember key concepts.
If you're willing to invest a considerable amount of money, I suggest buying Veritas' books. While not very good for learning strategies or tips in my opinion, I think they're great for question sources because they make their own questions and have about 14 books in total for each section of the GMAT. It should keep you busy and the level of difficulty varies, but I find it to be much more difficult than any OG's.
I recently bought the Kaplan Advanced 09-10 edition. This books is better for practice than anything. While it does give you detailed answer explanations for CR (some really tricky CR questions in this one, some debatable), RC and SC, I feel that their math strategy basically teaches you how to guess by plugging in values, which is not entirely bad. I heard good things about Kaplan 800 for practice and theory, but don't have any experience with the book so can't say.
Here's some things that I did to break the 600 mark, which took me about a month to do. My previous strategy was to blow through questions. But after the insightful Stacey Koprince wrote on article available on beatthegmat.com, I started taking more time analyzing the question than actually solving it. I walked through every single question and talked myself through the question. I would spend about twice to three times the amount of time reviewing than solving! And I did the same for practice tests. This was so beneficial, because by doing this you see how creators of the GMAT try to trick you! Also, I made cue cards of the those really tough questions and committed them to memory, but more importantly, tried to figure out how the GMAT would test this same theory in a different way, which means just be keen on the question and the lessons learned from it.
For math, my strategy for each question looked like this. Read the question, write down what I know, what I want and what I need. I can emphasize this enough, sometimes through all the calculations you can actually lose sight of what you're really looking for. Then I'd try to solve the question using the theory and strategies I've learned. I generally like to tackle questions algebraically first, and I ALWAYS double check my calculations while I'm solving the question. In fact, I write down EVERY calculation I do, and NOT do them in my head. If it becomes obvious at first glance or by a failed attempt that the question is very abstract, then I'll assign smart values and plug in play, or values from the AC's, usually start with D. Then worst case scenario, I'll guess. I noticed that the more theory I learned, the better I was able to eliminate answer choices, and make educated guesses. I was lucky on one CAT and guessed most of the questions that gave me trouble correctly.
I think that when you have a strategy to tackle a question that is completely different from the textbook explanation and yields a correct answer, then you are on solid ground. It means that you know the concept inside and out and can tackle it using varied approaches. Find the approach that best fits you and stick with it, but also know that there are other approaches and be ready to use them when you have to.
Even if you do know all the theory, it won't guarantee that you're in your target range. This is one point that I ignored for much of my prep, ENDURANCE. Test taking strategies are the primary recipe for a good score, but if you can't hack it for about 4 hours, then your performance will suffer. Take all practice tests with AWA, in fact I feel that the AWA helps to get my mind going, like jogging in the morning, warming me up for the harder parts of the test. Also consider what kind of snacks you will eat during break, you NEED energy. I usually eat a banana or some other fruit to keep my blood sugar levels up so I'm alert for each section.
Lastly, be confident. Confidence comes from solid knowledge of the theory but also in your test taking strategy. I used to let every single question I was unsure about get to me and put pressure on myself to get that higher score range, when I really should have been focusing on endurance and test taking strategy. If you feel uneasy about a question or feel like you got it wrong, don't let it get to you. What's done is and done and you can't change it. So don't let any stress affect the next question you do, because there will be more questions waiting to for you. You have to roll with the punches, know when to give up on a question and move on to save time for the questions that you can get right.
The GMAT is a beatable test. Every day of my prep I feel like I'm getting closer to my goal. Reading people's stories online on how they've achieved their goals also gives me inspiration and reminds me that this kid in high school, that got 52% in calculus can get a scaled quant score of 45 just by dedication and hard work. You can do it too!
Hope this helps and good luck!