When there are SERIOUS performance problems, i.e. your instance is totally pinned as far as resources go, the only way to log into the instance to do something about it is using DAC; even if you are on the same machine, if you’re trying to log in, as usual, it won’t make any difference.
Enable Remote DAC and save yourself from future troubles, now.
There are several problems. Better is to run client tools from a client machine and something like SSH or Powershell remoting to do things against a server itself.