They started around 2 weeks after Shadowbringers' release.
No changes coinciding with the issue.

I've not run a trace route during the ping spikes, as it usually takes longer to complete than the trace process (~30 seconds). Here is a trace route from just now.

Tracing route to 204.2.229.9 over a maximum of 30 hops

1 4 ms 2 ms 3 ms 192.168.7.1
2 12 ms 15 ms 9 ms 142.254.177.9
3 13 ms 11 ms 13 ms agg62.snaucaos01h.socal.rr.com [24.30.175.185]
4 14 ms 15 ms 14 ms agg28.cyprcabw01r.socal.rr.com [72.129.22.134]
5 30 ms 21 ms 17 ms agg27.lsancarc01r.socal.rr.com [72.129.21.0]
6 15 ms 24 ms 23 ms bu-ether16.atlngamq46w-bcr00.tbone.rr.com [66.109.6.92]
7 13 ms 15 ms 13 ms ae3.lsancarc0yw-bpr01.tbone.rr.com [66.109.1.43]
8 21 ms 16 ms 16 ms ix-ae-24-0.tcore1.lvw-los-angeles.as6453.net [66.110.59.81]
9 13 ms 14 ms 14 ms if-ae-2-2.tcore2.lvw-los-angeles.as6453.net [66.110.59.2]
10 16 ms 14 ms 15 ms ae-6.r01.lsanca07.us.bb.gin.ntt.net [129.250.9.17]
11 16 ms * 14 ms ae-3.r23.lsanca07.us.bb.gin.ntt.net [129.250.4.106]
12 23 ms 21 ms 22 ms ae-12.r22.snjsca04.us.bb.gin.ntt.net [129.250.4.150]
13 29 ms 29 ms 30 ms ae-40.r02.snjsca04.us.bb.gin.ntt.net [129.250.3.121]
14 29 ms 29 ms 35 ms ae-3.r00.scrmca02.us.bb.gin.ntt.net [129.250.7.11]
15 32 ms 31 ms 30 ms xe-0-1-0-1-1.r00.scrmca02.us.ce.gin.ntt.net [192.80.16.2]
16 * 32 ms 29 ms 204.2.229.234
17 26 ms 28 ms 36 ms 204.2.229.9