I arrived at the Qantas First lounge at approximately 6:45 PM. If I requested a shower in advance, then yes you are quite right maybe I would have a had a spot. But I wanted to enjoy my meal first before taking the shower and didn't want that to be interrupted when a shower were to become available. At the same time, I figured the lounge would have enough capacity to host shower requests without there being a huge backlog.
If there is any disorganization, respectfully it is from Qantas. I don't think it is unreasonable to expect that a shower would be made available to their First Class guests in a timely manner. In terms of cutting in front of people at the lounge, well ask yourself this, who would be entering that lounge? People in business or are Sapphire, well if everything is based on priority then I'm at the head of the queue. It's no different with Flagship First check-in with AA where you are escorted to the very front of the security queue. Some may find that rude and inconsiderate, but it's a perk for travelling so much. Now if there were other World Platinums entering the lounge to use said shower, well then maybe an argument could be made there that this was a bit inconsiderate. Then again, I would be expecting World Platinums to be doing the same thing.
There was no queue at TSA pre-check at TBIT when I arrived at 6:40 PM. It took maybe 2 minutes to go through that.
There is an escalator you can take on the left hand side that leads to TSA pre-check.