Yes, that is slow. Although maybe be due to chia default plotter being used (mostly is using just one physical core). I would forget about the default plotter, as it is rather worthless and focus only on MM. Start with one MM instance to get comfortable and move on to two and fine tuning when you will be ready.
I checked the specs of your setup. You can go up to 144 GB DDR3 RAM. I think that @RobbieL811 have just purchased rather inexpensive one recently (but a bit faster than yours - not sure it can be used to reach 1,600 MHz, though). I would upgrade your box to 128 GB of 1,600 MHz (if your 50 GB is slower, I would dump it). This way, your temp2 will be RAM, and your SAS temp1. Also, your box has 12 physical cores that run at 2.6 GHz, what is actually good. Although, those processors have rather small cache, what could be a limiting factor. I cannot tell how fast your box will be but would assume somewhere around 1 hour per plot or so.
Of course, all that depends on how many plots you want to generate. Still, the only upgrade you will need to make is to get that RAM (around $200 or so), and that is way less expensive than getting any other plotter.
Lastly, I didn’t plot for quite some time, so don’t really recall my MM settings (should be somewhere on this forum, I think), but you may want to search the forum to get the right thing (or someone will chime in).
Yes, the memory usage you mentioned is about right. Neither plotter is using much RAM. Where you need it is your temp2 folder (for MM).