The freezing may have nothing to do with the service at all, if the majority of the people using the servers are not having any issues then it can be a number of things that have nothing to do with the servers. Just because you have a new router has no bearing on anything. Read through this post I found on another site and you will see where the issues can happen and it has absolutely nothing to do with the servers having to much demand...
Here is a c/p from another site that explains the buffering situation.. As some of us are not experiencing the issue all the time:
What you have described is very typical of ISP capacity problems. This has been a major problem in my area where the ISP's lack either the total available bandwidth to cover its commitment or they lack the infrastructure to distribute bandwidth at full capacity. I've had people paying for 30mbps that at peak times would get less then 1mbps.
If you can prove your ISP is incapable of providing an acceptable service through logging speed tests over time you should report it to your local authority that is responsible for the regulation of ISP's. Then you should report to your ISP that you have reported them to the authority
That is xx mbps from your ISP to you but what happens between your ISP and the server? That is probably where the freezing comes from. Do a tracert and you will see where the freezing is from