That's far to fast to be thorough. As I understand it the complaint came from a group representing male victims of domestic violence who are sadly very badly treated by the UK legal system, so they're not really that random.
According to the article it was dismissed on the basis that the watchdog isn't allowed to investigate anything beyond personal conduct, that's a good example of why self regulation doesn't work. No wonder the legal system continues to be so broken if the watchdog isn't actually allowed to investigate.
So it doesn't prove or disprove anything about the sentencing decision, it just shows the system is out of control.
If the complaint is not about the personal conduct of the judge it is about the legal aspects of the case.
In which case the sentencing decision can be challenged via the appeals process.
If the CPS believes that the sentence was abnormally lenient then it can launch an appeal to have it reviewed at which point another independent judge will examine the case and th sentencing decision and, if they deem it necessary, change the sentence.
Of course this route is often used by the convicted in an effort to either overturn their conviction or reduce their sentence.
However it has been used by the prosecution when they believe the sentence was too lenient.
Suspended sentences are not unusual and it appears this case is not unusual other than becoming tabloid news