Derivatives is tough. However if you are finishing the mocks with 30-min to an hour left and skipping 2-3 derivatives vignettes then you will really be pressed for time on the exam because those 2-3 vignettes will take that extra 30-60 min. I wouldn’t skip over things or just guess on the mocks - take them serious. Otherwise I think it is just a trivial exercise. If you get to exam day and this is the year that Derivatives is 15% (3 vignettes) then the odds probably aren’t in your favor.
I have head the tactic of skipping/not focusing on a certain topic like portfolio or derivatives but for me I am not willing to take that risk. I did that once in college and studied everything for a comprehensive final but 1 area and thought to myself if I can get 90% on everything else I can just bomb that area and be fine. Turns out the ENTIRE final was that one concept I didn’t study. My luck with these things is horrible - which is why I don’t take short cuts like that because because knowing my luck if I skipped over Derivatives and Portfolio it would be the year there would be 5 vignettes on these two areas…