The practice test you're referring to are not useless, but yes, they don't reflect the actually test that well. The are useful if they are used as a means to review the material. Going over them will help to reinforce the concept you've gone over.
As for the PAT, I liked the Kaplan book for that. Especially starting out, when I didn't know how to do that stuff. They explain the answer better than other books. For example, they actually show you the 3D figure for the top-front-end section. So, I wouldn't write off Kaplan's PAT section. I thought is was very helpful starting out. Yes, the real DAT is a bit harder, but once you understand how to do things and have developed a strategy, it no longer about hard or easy. You can apply the same strategy you apply to an easy problem as you do to a hard problem. I didn't find Barron helpful for the apeture passing portion of PAT. But for the other PAT sections it was helpful.
Cliff is also a good way to study the PAT. In all honesty, the Barron (except appeture passing), Cliff and Kaplan book's PAT section are a really good reflection of the real DAT. I don't understand why people keep saying it's harder. The shapes are different, the idea is completely the same. When you are practicing the goal is to figure out how to approach the problem. For instance, in the cube counting section, are you going to count the cubes from right to left or from front to back? Are you going to count the cubes at all in that section or not? Stuff like that, it doesn't matter if it's hard or easy. Use all the resources possible and don't write them off because of what people have written. The real PAT isn't as hard as people keep saying. I studied, I had no clue how to do it. I used those resources and got a 20. So, you see the real DAT's PAT can't be that bad. Maybe it's easier to blame the resources than it is to blame yourself for not studying. (Perhaps there are people who try really hard and simply have a hard time. I'm not talk about them.)
Use all the resources you can get your hands on. They can only help in the long run.
Biology: Is hard because it's random. Much of it is not covered in Kaplan. (80% is not covered, maybe even higher.) I was able to get through this section by using AP review books (get them @ the public library) & some questions I was able to answer because of the biology classes I've taken.
Good Luck.
