I've occasionally heard people describe their test in a similar way (reporting that they saw longer-than-expected Quant question stems), so that can happen, but it's unusual. If you retake, which I'd certainly recommend because there's a lot of evidence you can get a much higher score, it's not likely you'll see a similar number of very long questions. In fact, you might have seen longer questions because you weren't scoring as well as you usually do, and therefore weren't seeing questions that were as hard as you usually see -- I find they often make medium-level questions longer or more computationally intensive than high-level ones, so that the time you spend reading and solving a medium level question will be similar to the time you need to think properly through a hard one.
Any one test score is affected by luck. That's partly true because most test takers need to guess at some questions, and guesses can go well or go badly. But it can also be true because of content balance. If you're better at some question types than at others, you might have good luck and see a lot of questions you're good at, or bad luck and see a lot of questions you're weaker at. The test has no way to know what you're good or bad at, so if you felt on test day that the test was giving you "types of questions I'm worst at", you simply experienced bad luck on that test.
The good news is, bad luck isn't likely. Roughly neutral luck is the most likely situation, and good luck is as likely as bad. From your recent diagnostics, you appear to be a Q48/V42 level test taker, roughly. If you could take a real test tomorrow, you'd probably get a score very close to that. That's assuming you perform on the real test in a similar way to how you perform on diagnostics. The discrepancy between your diagnostic and test day scores is large enough that I'd be a bit concerned about that. One thing you could check: was your first test score (the 700) in line with your diagnostic scores? If so, and if you have no explanation (fatigue, anxiety, distractions, etc) for the anomalous 680, then it's probably just the result of bad luck. But if your 700 was also lower than your diagnostic scores, you might want to reflect on your test day performance, and ask whether you might be doing something differently. If you're rushing because of adrenaline, or making careless errors because of stress, say, then that will be an important thing to address before a retake. But if you think your test-taking is fine, I don't think you need to do all that much before trying again, if you'd be happy to see a Q48/V41, say.
And I have prepared a lot of Quant material specifically for test takers near the top end of the scoring scale, so if you're looking for a good supply of realistic challenging practice questions, feel free to send me an email at the address in my signature.