Is special task force exists?

[Vnolan]

The problem "was solved" when they posted a video with OBVIOUS humiliations of our group on YouTube. BUT only one guy get 9 days ban for posting this video.

How do you know for sure that's what happened? That would go against "SE doesn't accept outside sources".

How many proves we need to gather to make STF notice this big problem like "radar using to get an anfair advantage"?

Don't bother with the STF. About the only thing they do is deal with those RMT bots with gibberish names. They can't detect hunt radar (or anything else really) so you'd have to submit proof to the GMs. Contact a GM in game and ask what proof you would need or explain the situation and ask what you can do. If they redirect you to file reports to the STF, ignore that, since as you've seen, it's a waste of time.

What is radar -- some 3rd party app?

You know how monsters only load in as you get close to them? S ranks don't require you to be near and will load in once they spawn and are visible from anywhere in the map. The third-party apps are able to detect the S rank being loaded and provide a signal to the user. A prank that used to be done was to rename your chocobo to that of a hunt, summon it and watch as the radar users would rush to your location.

One of the first searches of hunt radar gives you another forum thread:
Radar for hunts, is this fair? Take a look.

That's over four years old. It was closed within 12 hours of being opened with the generic "report to the STF for further investigation" comment. Since then, has SE done anything to prevent the use of radar or change hunts so they can't make use of them? No. Hence, the Devs don't care.