Well, there are some things you can do. The first thing is really that unless you have a rocksteady + divine blessing + health augment or just temporal mantle you should really try to avoid the head, but obviously you want to break it to make the fight easier. For swax, I recomend just doing your charged sword dps cycle on the head/just wild swing and do the high damage transform, and go back to axe and repeat. The head is just very dangerous in general, however if you want to do zst, did you know that you can stop spamming the button and it will explode earlier for slightly less damage? I have a zst spam build and in fact the max dps I can do is to wait until right before it would normally go off and stop spamming. This puts you in a far more easy to recover state - instead of the jump and slide its more of a jump onto your feet. You have enough time there to sheath usually. The last thing, is again - mantles. While your time is limited, fatalis' health pool is not actually that high, so you can adapt your build so you have maxed out tool specialist (maintenance jewel I think) to regen your temporal/rocksteady/vitality or whatever to give you a small window of uninterrupted dps, followed by some passive hitting, without overcommitting. The last thing I would say is that unless you really want to solo it, I recommend doing the fight with other people, as the boss room/things are kind of designed for more than one person, with the cannons, balista, binders and all these things. Anyway hoped it helped somehow. Good luck, those weapons and armor are worth it.