Comcast... before changing DNS on my network, I tested a variety of DNS providers including Comcast. While Comcast had the best individual test minimum and average times, Comcast repeated testing showed lost packets and the occasional worst max times.

I don't know why they faired as poorly as they did, but once I realized some network issues could be pinned against DNS packet loss / terrible performance spikes, I changed over to 9.9.9.9 and 8.8.8.8 as the fall back. Home network has been a bit more stable since the change over.