Question regarding VH Zarth full break and attack pattern

Hello friends

1) I had been farming at Zarth for a while now and VH is quite easy to kill without FB.
But FB is nessary to get more rare drop. However, everytime I tumble him there only 2 second circle and it gone. And I believe it is 1 minute before you can tumble or flinch again? The run dragged on for like 5 mins and we cannot get full break. Is there an easier way to FB this boss?

2) As a tank, most of Zarth attack barely make much damage but he has one hell of a string fractional damage atk (30% of hp) With one wave, I am down.
I still cannot tell his attack pattern. How to regcognize that he is using that atk? I think it is a red area that look like a fan and I should run behind boss to avoid damage?

3) Zarth always running around to the cornner of the room. Pretty similar to Usasama. Is there any specific area that I should lure him to prevent him from jumpinh around so much?