In a fair draw you should see the top 4 play 2 of the other top 4 from previous year and bottom 4 play 2 of the other bottom 4 from previous year. However with some scheduling requests mainly around ANZAC day being at the beginning of the year and some other requests in the middle this would be more difficult to achieve hence there are some irregularities.
I think in our case we have played Balak and Mallala 3 times for the past 2 or 3 years, and it appears as though our fixture is identical to last years (same teams in the same sequence) so it could be possible that the league took a simple option and reused last years draw and made some small tweaks here and there.

PS: This is definitely not a complaint, I love playing against Mallala (even though we lose most of the time) and our last 6 games against Balak have been ridiculously close each time which are great games to play in (be nice to win more than 1 of 6 but ah well).
If you don't like it, change it. If you don't want to change it, it can't be that bad!