I am fanatical about eliminating ads.
Network-wide (hardware) ad blocking is the only way to broadly block ads and spam, including banner ads on apps on your phone, google and facebook embedded ads, and ad trackers.
I see zero ads, until I leave home, then I will see ads for things I have been searching while at home (from cookies).
My blocking is so severe that I can't even access referral / redirect links.
I too am interested in the OP's question. My current setup:
1) Netgear R7000 running FreshTomato AdBlock script (running as a LAN switch only, using ASUS Merlin Wifi router, and network drive host/media server)
2) DNS managed by a Raspberry Pi running PiHole, blocking domain name lookup requests to known ad sites
It seems that both my methods are using DNS blocking / masking, so I could probably eliminate the older FreshTomato.
The only thing that isn't blocked fully by the above are youtube ads.
I also use browser add ons like ublock Origin, Adblock, AdNaseum, and Ghostery as well.
If you see some of the screenshots from pi hole posted above, one user has over 43% of network traffic blocked as spam/ads. You can actually double your internet speeds just by bypassing ads!
From what I can see Diversion and Unbound are two options for AsusMerlin. But they are using the same DNS blocking scheme.
Is there any added benefit these would give you, above and beyond the Pi Hole?
I understand OP is hesitant to use a Pi Hole, but I *HIGHLY* recommend it. One time purchase of around $60, and it is 100% dedicated to running as a DNS server, so there's no impact to your main router's performance. Also highly configurable and well supported / updated. I don't think I've rebooted or touched mine in 3 years. It just works.