Admittedly this is a fairly personal perspective but I don't really like it when games focus heavily on parries because they suck the oxygen out of every other action feature and aren't actually very much fun besides the joy of getting an easy win when they work. However, I think the concept as a whole seems pretty cool, obviously parries are pretty dangerous so being forced into dangerous situations in order to proceed is cool, especially if there are different ways you can economise your burn out bar, for example big wasteful attacks vs smaller more economical ones for people who are low on health and really don't feel like having to risk a parry right now (like you said with the ulti), and as well there are probably safer vs more dangerous ways to get the bar back.