run tracert to one or more of the servers you are using. You need to see where the latency goes up a lot.
Most times you will see the issue in the first or second hop of the trace. The first being your network in the house normally a bad wireless signal or in the second which which represents the connection from your house to the ISP. You need to check all the wires and then call the ISP if it is in the second.
The bad news on this particular one is it could be in the internet. If you see the latency jump and it is many hops from your house then it is likely in blizzards network. They have had various parts of their network under denial of service attack since they released their last update. Not much you can do .....so maybe you get lucky and it is a problem with wireless interference.