If you do a quick search across the forums, going back years, you can find many threads with users seeing similar problems, including a large megathread about this created by steinberg themselves. I think there may be similar threads for older versions of cubase, but the base issue and behavior are the same.
https://forums.steinberg.net/t/cubase-12-0-20-performance-issues/
Have you tried 1) disabling all virtual cores (hyperthreading) in your BIOS, 2) disabling ALL CPU power management (p-states, speedstep, etc), and 3) locking your CPU to its highest rated speed?
Try this, and then try C11 (or C12, or C10, or C9) again with ASIO on or off, depending on where you see the best results. Do you still hear/see the internal ASIO overload and hear the audio pops/glitches/dropouts?
I have been tracking this issue across 3 PCs/laptops, and across cubase versions since 10.
I am also aware that hyperthreading has caused problems on cubase since the early 2000s, when the Core2Duo first rolled out. I have seen IDENTICAL problems with ASIO overload on any Intel / Windows 7 or 10 PC or laptop I have built, and with every current(10, 10.5, 11, 12, 12.0.20) version of cubase.
The ONLY way I have been able to reduce this behavior has been the above config (disabling all power management, and on 2 platforms, I had to totally disable hyperthreading).
Right now, on my fully updated x299-based win10 platform (i7 7800x CPU, 32GB RAM, focusrite 8i6 gen3 interface) the magic formula is:
-disable all power management
-lock CPU at max clock speed
-enable hyperthreading
-ASIO Guard set to normal
This results in MOST of the ASIO overloads stopping. I will occasionally still see random spikes to 100% with an audible pop/click, and when this happens Ive learned I can toggle my audio interface buffer to anything, from anything, and that overload does not come back for that session. I have no idea why, but it works 100% of the time for many months. It may be that resetting the audio interface is the trick and has nothing to do with buffer.
On my other systems (2018 MSI laptop with an intel i5, also an older 2008 x58 chipset desktop with an intel 965 extreme CPU), I have to fully disable hyperthreading to avoid ASIO overloads. I spent many hours troubleshooting other configs and settled on:
-all virtual cores disabled
-power management on/off doesnt matter as long as HT disabled.
-turbo or speedstep, also on/off doesnt matter as long as HT disabled.
-ASIO guard OFF (turning it on adds massive latency and isnt fixing anything)
Ive read these forums and the posts about this issue for years, and I can count on the fact that any time I visit them again, after any length of time away, people are posting about the same issue and struggling with the same troubleshooting and configuration testing to get it to work. I am solidly of the opinion that this QA work should be done by steinberg, should have been done long ago, and a SUPPORTED + UNSUPPORTED hardware and software list should have been created. This is endlessly frustrating to me.
I hope something works.