Jetstar StarClass got me to WP1 with multiple trips to Japan, which we would always pick up during their excellent sales. From memory, we paid $400-$500 each way which was a no-brainer for leisure travel OOL/CNS-NRT/KIX.
However, since they took away SCs from Business fares, we haven't flown with them at all, and instead use Qantas JASAs + also buy Qantas J flights when they are (briefly) on sale.
Having said all of the above, if no other reasonable flight option presented itself, I would buy the Business Max fare for the SCs.