well lucky for them we only worry about this with drugs that there is a narrow therapeutic index with. There was an episode on House MD that covered this with a drug that only worked in "black people" (no racism intended here), in typical TV fashion, the guy was offended that his drug didn't work in white patients or something like that and he wanted a different med. Luckily, we use genomics here to genotype these sorts of things or various other tests that one can do. Certainly drugs like aminoglycosides, warfarin, phenytoin, lithium and others, which are used more often then not require a careful consideration of kinetics.
im not going to argue the difficulty and importance of therapeutics, but a preceptor once told me, its the kinetics, its what happens in that time between administration and end result effect that separates you from doctors. They wont understand it and won't bother, this is your chance to shine. Its harder then therapeutics at our school, maybe because we specialize in it. It may also help in making therapeutic choices such with comboing imipenem with cilastatin (Primaxin). Cilastatin blocks the metabolism of imipenem which leads to the efficacy of the antibiotic.
Therapeutics is difficult because you are forced to make a decision on the patient when all the cards are laid out. Its not about memorization, its about taking the case into context and what is best for the patient. There is no memorization here, and maybe thats why its difficult for people. But if you know the options and you know the patient, the choice may be just that much simpler.
the more important message from comparing the classes is that school isn't a fact finding mission. its not memorizing everything for 4 years. Its more then that.