Poorly organized code on the best servers still performs poorly. It is not the hardware but how everything is coded. Zos has continued to add to the server load without organizing the code.
The AF issues are a great example. Zos built it to handle dungeons then added BGs on top of that. After two years of not being able to fix it they build a new AF but still have one handling both dungeons and BGs. The hardware is not the issue.