Can you provide more insight as to which sample problems you are doing/which exam you are planning to take? Kind of difficult to provide anything of usefulness without more info.
However, judging by what you have given, it appears you are planning to take a Civil exam and I assume the WRE depth. While I cannot speak on the WRE portion, I would highly recommend registering for a review course. I cannot speak on any others but EET's course(s) were fantastic and a huge help on the exam. Their breadth course does a good job of filtering out the "fluff" and teaching to the exam topics. I assume Dr. Nazrul is the WRE main instructor for WRE depth. He taught the "water" related breadth topics and does a great job simplifying the material and is very thorough.
I know many people have "blind" studied and passed but I think a guided/structured study patter via a review course is probably the best use of your time and ensures you don't waste it on topics you don't need. And, in general, look at the list of topics covered from NCEES and put more focus into the bigger category questions. I'd be much more worried about a topic with 7-8 questions than one with 1-2 questions.
