The interesting thing to me is that despite having 5M domains in their blocklist, they only have 8.2% of requests blocked. My dashboard currently says 36% of requests are blocked while having 125k blocked domains.
I'm interested to see where you get your lists!... mine[0] is about 51k domains, and I don't see ads.
You might want to check if it's Firefox, VSCode or some other telemetry that's getting blocked. I had a similar percentage blocked until I disabled those apps phoning home.
Yeah, on our Pi-hole 45% of the blocked domains are only four domains. Three Microsoft at about 35% and one Google at 10%. But we also have uBlock on everything that accesses internet so that lowers the amount of google lookups.
pi-hole shows blocked DNS requests, it doesn't show the the number of the AJAX/Static request your browser tried to make, which is going to be quite larger and that may match your 36%.
The developers of pihole (at least some) don't use anything but the defaults