u can sort of argue there is scaling, e.g u need about a 75% to get a 7 in Maths HL but need 90+ for mandarin ab initio
i did IB for half a year in year 11 and screwed up my language so i dropped, if i didn't have to do a language, i would still be happily doing it.
u have take a maths subject, english subject, 2nd language, humanites, science and an option
the depth they go into each subject is alot further than in the HSC but its alot more work, most subjects go into 1st year uni and the highest maths course even completes 2nd year uni (2 guys in the history of my school have taken this course)
physics has 4u level maths in it, no joke in prelim u do circular motion with the angular velocities etc
english, the lowest lvl level u can choose is above eng ext 1 level, u have tests where u analyse texts in the exam and write essays on them
language, i did mandarin for beginners and it aimed to have u learn basically the whole language by then end of the course, levels above that have u writing essays and short stories in the language
if u cope its rewarding though, most people who don't drop out get >95 UAI(atar now) and u get a lot of experience in all areas