Timing violations on SignalTap II Analyzer

If you have unrealistic requirements, the fitter will still try to meet them(it has no idea what's realistic). It's possible that could hurt your real requirements, although more often than not it won't. You need to analyze your failing paths. If the only failing paths are these ones you would expect to fail, then it didn't hurt, but if other paths suddenly fail and they're part of your design, then that's a problem.