Haven't you noticed any drastic reductions in speed?
My rpi 3b (not 3b+) just couldn't handle it. It had 2 users. Our DNS resolution times increased by about 200ms. It was awful. I stripped it back out and haven't bothered trying to set it up again.
(Other details: the RPI was hardwired, wireless disabled, and it was a fresh raspbian install with zero customization outside of adding pihole.)
I would say that you may have a setup issue with your router. My resolution times decreased when the pi-hole is providing DNS responses. I have 30+ devices on a 3b+.
I'm using a UniFi setup and both WAN and LAN point to the pi-hole local ip address.
I'm running a pfsense setup with cloudflare as my DNS (DNS-over-TLS, in specific). As soon as I had the rpi in the middle, it jacked up resolution times like crazy (rpi was set to use my SG as its DNS, so <clients>->rpi->pfsense->1.1.1.1
It's good to know you guys haven't been having problems; I thought everyone was just fucking nuts or something, but no; local problem. Sigh.
Ugh. I tried. Somehow when I first configured it, I configured something incorrectly - and it literally stopped all connections to or from the router entirely. I had to physically connect to it and uninstall the pkg to get it to work again.
I wanted to try it again and NOT do what I had done previously, but I think a conf file is still floating around because the second I install pfBlockerNG(maybe -dev too? I actually can't remember now), my entire network instantly goes down and won't come back until I remove the pkg again.
I don't know enough about BSD's package manager or where pfsense puts package conf files to try to track this down and stop clean it out. I'm sure I COULD figure it out, but I have other projects that are higher priority :)
Edit: I should also note when I was trying to figure this out I had a very angry spouse standing behind me burning holes into the back of my head because the network was down, so I didn't make a priority of really looking through logs and trying to properly diagnose things. I just wanted things to be up so that I wasn't slain.
I have my router setup to act as a dns resolver and cache, with the pi-hole (rpi 3b) upstream. This fixed my speed issues as only a few queries actually make it to the pi-hole.
The router has a secondary dns server as well in case the rpi goes down (which has happened ~2 in the last year or so) or I need to fiddle with it.
I have an old desktop in my basement running Ubuntu with PiHole (and some other things). My router is still the DHCP server, but distributes the PiHole machine as the first DNS server. I haven't noticed anything being slow.
My rpi 3b (not 3b+) just couldn't handle it. It had 2 users. Our DNS resolution times increased by about 200ms. It was awful. I stripped it back out and haven't bothered trying to set it up again.
(Other details: the RPI was hardwired, wireless disabled, and it was a fresh raspbian install with zero customization outside of adding pihole.)