From the Pi-hole logs in the other post @ archlinux, it looks like your running an open resolver ?
pi@noads:~ $ whois 80.82.77.139
country: SC
pi@noads:~ $ whois 52.73.169.169
Country: US
https://umbrella.cisco.com/blog/2014/03/17/dns-amplification-attacks/
On a Linux or Mac client PC, whats outcome for below one ?
cat /etc/resolv.conf
On a Windows client PC, whats mentioned in the DNS section when run below one in a CMD prompt ?
ipconfig /all
Are they displaying the Pi-hole IP address as the only DNS server ?