I have a theory on why ST perf is always the most important metric for me, and some other folks. When you're waiting for something synchronously, like rendering a webpage, stuff to open, etc. you're usually running a ST load. For stuff that can benefit from multithreading it's usually planned task. So does it make a difference if it takes 4 minutes compared to 3? You will still context switch.
Right now I have ~20 tabs open and a few apps, a workload which is probably similar to the average user. My machine currently has 510 processes running with 2379 threads, though most of them are background. I'd wager core count is more important than ST performance nowadays, especially considering the fact that applications seem to be multicore optimized.
I’d check your activity monitor to see how many of those are sleeping. My suspicion is that most of them probably are, likely to the point where you are using “less than a core” to handle the load.
