In my case today, traceroute indicates a significant latency spike at Hop 10 (ae2-br02-eqam1.as57976.net, 220–251 ms) within Blizzard’s infrastructure. The other hops show low latency, so no issues on my end or with my ISP.
The same as57976 was causing issues back in 2020 in this old post Seriously, can you fix your servers?