This is more of a connectivity problem than a gaming problem. Each individual should run some tests to determine their latency to given servers.
First, run a continuous ping from your computer to your ISPs primary DNS for about an hour (in windows, use ping -t ). When complete, check the minimum, maximum and average. All of these should be about the same and should be no more than about 100 ms. Battle.net does not have ICMP enabled, so you can't ping each individual server directly, but you can run a traceroute (tracert uswest.battle.net) to see each individual hop along the way and see how you are routed to that particular server. You can alternatively use pathping to get more detailed results about latency to each hop along the way.
Once everyone has run these tests you should be able to compare results and see which of your connections is providing the high ping times. If those pings times are on the network side of their ISP, they might be able to get their ISP to fix the issue. If the high ping times are the result of a bad route or server elsewhere on that route, they may be able to appeal to their ISP for a re-route, but don't hold your breath on this option.