Can someone explain feral tanks with tsunami/madness?

I dont play feral myself so I might be wholly misinformed, but this seems grief as fuck no? Is it for when you go cat on bosses?

As for main tanking does it stop people from ripping threat 5 seconds into the fight or? Or do you want it so you can consistently keep threat on the few trash mobs the prot pala might not be tanking throughout run?