Tested this with a tank using 5 piece footman and 5 piece juggernaut armor sets and immovable brute to give me the ability to survive multiple hits from various damage sources. My damage mitigation is at 50% spell and 40% physical without buffs so I can take mitigate a lot of damage. With the visual swirls actively showing immunity, I would continuously get feared, wrecking blow knock-back, invasion knockdowns, knock-backs with talons and various other forms of soft and hard cc's stacked on top of each other.
The initial using of brute or breaking of the hard cc works fine with the immunity timer but if cc's are continuously applied while your immunity expires and you try and get another the immunity bugs out and stops working, meaning you are not granted immunity the second time however the visual swirls continue to fire off. Once the immunity timers expire the process repeats itself. This might be a result of the nerf Immovable received in in 1.6 where the timer was reduced from 15 seconds to 5 seconds on just the cc immunity of the ability with only immovable potions keeping the original 15 second timer. Working as intended so you cant stack immunity or a broken active skill?
With the current time to live being so low I would suggest restoring the timer back to 15 seconds with the change from 1.5 version being in order to use the ability, 5-pieces of heavy amour need to be equipped.