I noted about 4-5 weeks ago there's D class all over the place for most of the rest of this year on SYD-YVR - I've never seen so many ever available before. A lot of them seem to be gone now, but there's still quite a few showing available over random date checks.

For the OP, firstly welcome aboard FT and secondly, I suggest you search YVR-SYD-YVR first and find out the days when regular D is showing available. Then try and build a YYZ connection onto it - multi city search may work best.
Like the regular fares on SYD-YYZ, the YVR-YYZ portion of the flight often mucks around with the availability on the through portion of the journey to/from SYD.