Very true - one can easily work out what is needed using simple rules of thumb. Max drift = 1/3 of wind (at 120/140kt), and VS for climbs/descents is 200ft/min for each 1000ft to gain or lose (10nm to run). In 600hrs I haven't yet had to know more, but to be fair the GPS displays all esle I need.
Which makes a mockery of the sub-1 degree precision required from the circular slide rule in order to choose the right multiple choice answer in the nav exams.