From my reading it appears Singapore Air have had 5 oil leaks on the A380, compared to 2 on Qantas. Excluding the major A380 issue Qantas had.
Qantas chose to shut down an engine, whilst SIA didn't.
So what does this mean? Qantas are more conservative, safety conscious etc. Or maybe that the SIA issues weren't as severe.
We can only speculate, but I agree that issues on Qantas get publicised more frequently than with other airlines.
Personally I haven't noticed a deterioration in service with Qantas, and feel safe flying with them.