I will have to watch a video to remember which fight it was, but even before Leap slam I was able to find what attacks I could take the chip damage to get in stun attacks and then would get 2 full rolling attacks once they were stunned.This fight is prior to Leap Slam being available. It is barely past where you can get your first lvl 3 gem and even have access to Shockwave Totem. Even if you have all that, though, there is *literally* no downtime from boss attacks to allow an attack. That is just bad design when you are going for this type of punishing game play. And that is even in the first phase of the fight, as it gets more intense the only time you are even able to reliably get close to him is when he rushes in with 5 quick attacks before immediately going into the next attack animation. I actually think the fight has great mechanics, but it is not properly tuned for all classes and their abilities at that point in the game.
Idk, could have just gotten lucky with gear drops and overleveled a bit but not intentionally, I just have been taking my time and full clearing, for the most part I'm usually around 1 level over the monster level of that area.
Edit: I also had a decent amount of life regen on gear so I'm sure that helped, too.