ISP: Verizon FIOS
Location: Long Island, NY
Time of Occurrence: Pretty much since Maintenance 2.1. Seems to mostly affect Dungeons/Raids.

WTFFast appears to resolve it most of the time. Lag got so bad tonight I DC'd (with WTFFast).

Trace:
Tracing route to 199.91.189.57 over a maximum of 30 hops

1 <1 ms <1 ms <1 ms Wireless_Broadband_Router.home [192.168.1.1]
2 6 ms 7 ms 7 ms L100.NYCMNY-VFTTP-116.verizon-gni.net [173.68.109.1]
3 11 ms 9 ms 10 ms G1-15-0-4.NYCMNY-LCR-21.verizon-gni.net [100.41.192.118]
4 7 ms 6 ms 6 ms ae5-0.NY325-BB-RTR1.verizon-gni.net [130.81.163.208]
5 8 ms 10 ms 9 ms 0.xe-4-0-0.BR3.NYC4.ALTER.NET [152.63.23.173]
6 25 ms 30 ms 27 ms te-7-3-0.edge2.NewYork2.level3.net [4.68.111.137]
7 35 ms 34 ms 34 ms vlan52.ebr2.NewYork2.Level3.net [4.69.138.254]
8 34 ms 34 ms 34 ms 4.69.201.37
9 33 ms 35 ms 34 ms ae-5-5.car1.Montreal2.Level3.net [4.69.141.5]
10 * 197 ms 210 ms ae-11-11.car2.Montreal2.Level3.net [4.69.141.1]
11 36 ms 39 ms 36 ms ORMUCO-COMM.car2.Montreal2.Level3.net [4.59.178.74]
12 36 ms 36 ms 38 ms 192.34.76.10
13 33 ms 34 ms 34 ms 199.91.189.242
14 33 ms 32 ms 32 ms 199.91.189.57