Blizzard has now fixed this issue for their games (thread), the problem seems to be with a middleman provider called Level 3, and affects Verizon/Cablevision users. It's not a throttling or Net Neutrality thing. See the traceroute below and threads on BattleNet forum(s).
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\LHTECH>tracert 104.160.131.3
Tracing route to 104.160.131.3 over a maximum of 30 hops
1 <1 ms <1 ms <1 ms 192.168.1.1
2 1 ms 9 ms 8 ms lo0-100.WASHDC-VFTTP-342.verizon-gni.net [72.83.
247.1]
3 11 ms 11 ms 7 ms B3342.WASHDC-LCR-21.verizon-gni.net [130.81.16.9
2]
4 Request timed out.
5 4 ms 9 ms 9 ms 0.et-5-3-0.BR2.IAD8.ALTER.NET [140.222.239.87]
6 11 ms 9 ms ae17.edge1.washingtondc12.level3.net [4.68.62.13
7]
7 Request timed out.
8 114 ms 117 ms 117 ms 4.16.252.202
9 116 ms 117 ms 118 ms 104.160.137.35
10 128 ms 128 ms 104.160.131.3
11 126 ms 130 ms 133 ms 104.160.131.3
Trace complete.