I use Windscribe as a workaround which works for me.
This is a WAVE problem as I have experienced it before. You have to be insistent that you get this problem passed along to a higher tier of support. If they tell you a technician needs to come out you tell them, “Yea you need to connect me directly to your supervisor as you cannot assist me”.
Think of connecting to Blizzard like driving down the highway, many cities(nodes) in between your destination that you have to drive through to get to Blizzard. One of those cities(nodes) is completely closed off and you are sitting on the highway unable to move forward or go around the city(node). Using a VPN routes you through different cities(nodes) to get to Blizzard bypassing the troublesome city(broken node) you cannot get past.
You can refer this post to Wave Customer service if they need an explanation and tell them something is wrong with one of the nodes along the way to the Blizzard servers. Explain you are experiencing HIGH LATENCY while playing the game but using a VPN solves the issue which means it is on their end or their peering partners. Make sure to note you are not the ONLY WAVE customer experiencing this issue so sending a Tech out to your house is useless, reference this post once again. BE FIRM and INSISTENT with them as they will try to do useless troubleshooting with you to solve the problem.
Edit to add: Gotta love WAVE forcing a modem reset before we can talk to Tech Support!
Edit again: Contacted Wave. Wave claims its outside their network while Blizzard claims its outside their network. Wave did put in a ticket but we need help BLIZZARD! Please, I encourage everyone to CONTACT WAVE! I know the hold time sucks but the more people we put pressure on the quicker they get off their butts and help us.