I am a patent agent who will be attending law school next fall, so regarding patent law, I know from experience.
Generally law schools do no teach you patent law (although you can take IP classes, including patent law). You learn it on the job.
Yes, you have to take the "patent bar" exam, and yes it has a low pass rate, but it is not too difficult as long as you study and are prepared. My guess is it is no harder than a regular bar exam, which as future lawyers we will all have to pass.
It is also true that most patent agents or attorneys in the biotech field have PhD's, or at least a masters, but that is not true for all technologies (in fact biotech is really the only one that applies). I have a bachelors in Chemical Engineering, and I have been very comfortable in chemical, mechanical, basic electrical, structural, and computer software cases.