There is also a series of videos by Zeiss on the Axioscan here that might be useful: https://www.zeiss.com/microscopy/us/local/zen-knowledge-base/axio-scan.html
Unfortunately, I am not experienced with other dedicated slide scanning instruments, so I cannot address those comparisons. My perspective is from operating the Axioscan as a drop-off service for bulk slide imaging, so the time that the instrument takes to finish is usually not critical to researchers, except those scanning slides that require further processing after the scan. The 15 minute scan time doesn’t sound unreasonable for tissue of that size, but it might be a bit slower than necessary.
In the tissue detection step, make sure that you are minimizing the amount of empty/unneeded space that is being scanned. This will save time during the coarse focus, fine focus, and scanning. It will also improve the accuracy of the focus maps. The empty space is probably already being minimized, but I’ll mention this for the sake of completion.
In the Axioscan, brightfield scanning has far fewer variables than fluorescence scanning. Perhaps confirm that your coarse/fine focus range and interval are following the Zeiss recommendations in the video/manual. The default adaptive focus point strategy should be relatively fast as it uses no more than 24 reference points in either coarse or fine focus (fewer for small samples). Changing the focus point strategy could save you some time during the focus steps, but will likely require more sample-by-sample fine-tuning. In the exposure section of the coarse/fine/scan steps, flash duration should only be a few microseconds per image with good illumination intensity (on our setup, your equipment may be different). If you optimize speed for a specific sample, the scan profile may be less robust or even fail for other samples, so please be careful and ask your Zeiss rep about any change that you are unsure of.