I scored Q45 and yet that was only 74% and my V41 was 92%.
Actually, it has always been the case that the quant and verbal scales are simply different. (I don't know why they made the scales different in the first place, but they did.)
Yes, cheating does factor in, although the GMAC folks are pretty good at making it really difficult to cheat and at catching cheaters. Some guy may have a photographic memory somewhere, but they don't let you just keep taking the test over and over again - they would have banned him by now for too-frequent test-taking. (Yes, they actually do this; I know plenty of teachers who have been banned, not for any dishonest activity, but simply for trying to take the test too frequently. They basically send you a letter saying that they will not let you register again until you explain to them why you need to take it again.)
The bigger issue is much more mundane: many more international students, people for whom English is a 2nd language, are taking the test now than were ten years ago. Someone speaking English as a 2nd language is going to have much more of a disadvantage on verbal than quant. In addition, US math instruction is simply not as good as math instruction is in lots of other countries; the average-level quant skills of someone coming from certain other countries will be higher than the average-level quant skills of a US student. As more students from these other countries start taking the test, the overall ability level of the quant pool rises.
how hard is it to improve from 710 to 740?
The higher you go, the harder it is to improve. That's at the high end of the scoring range, so it's a lot harder to earn that 30 points than it is to go from, say, 510 to 540.
I am going to take a good guesses on about 30% of the questions from 1-27 to conserve time to average about 1.6 minutes per question. Then, I am going to focus on getting the last 9 questions correct with the extra time that I have since they all count towards my score. Do you find this to be a winning strategy?
No. Sorry. :) It is not true that the last 9 questions all count towards your score - not necessarily. It's also not necessarily true that the first 9 questions all count, or that the earlier questions count more than the later questions, or any of that stuff that you may have heard. People like to think that there's a way to "game" the test, but there really isn't.
Your best strategy is to work steadily through the test, giving adequate time to each question but not spending extra time unless (a) that extra time is definitely worth it, AND (b) that extra time isn't more than about 30 seconds.
By "definitely worth it," I mean: I know exactly what to do, I know I'm going to get this problem right, it's just a little longer than usual for some reason, so it's going to take me an extra 15 to 30 seconds. I'm NOT using the extra time to "figure out" what's going on or how to do it - I already know exactly how to do it. It's just going to take extra time because it's longer than usual - more to read, more steps to do, whatever.
If I need more than 30 extra seconds, then I'm better off just picking something right now and moving on.
If you find yourself behind on time by more than 2-3 minutes (overall, in the section), make a random guess on the next very hard question that you see. If you find yourself ahead on time by more than 2-3 minutes, start making yourself write your work out more fully, or double-check your work or whatever, but slow yourself down.