I'm in the same situation except my marks went down by A LOT.
I fucking put effort into 1903.
I don't fucking understand.
Ugh.
The exams are worth so much that if you screw something up it can effect your mark a lot. This becomes even more evident in second and third year when a lot of them have 75-80% exam components.
Beyond that I have a vague feeling that they have reduced the amount of scaling in the Advanced units in recent years. I hear from graduates that they put in very little work and got HD's. This doesn't seem to happen anymore, the raw mark you get seems to correlate well to the final mark. Also note that some class definitely scale DOWN in second year, in particular the NORMAL financial mathematics class.
Also there are sometimes mistakes in the exams in which cases they give extra marks to everybody. This happened last year in 2965 when Galloway wrote one of the questions incorrectly, it resulted in everyone getting very good scaling. Conversely something like 2968 is tough for everyone and even very good students struggle to get distinctions.
Look at it this way, if you want to do honours in mathematics and statistics you only need a 65 in advanced units or a 75 in normal units.