Thinking back to the Flame Instigator fight in DT1. All his actions were somewhat randomized, but depending on what was happening, certain actions had a much better chance of occuring than others. At the time, I felt that was okay. Had I made that today, there would have been more to his decision making and no random elements would be around.
Looking at Death, he has 3 scythe swings that can be chosen, in a combo of 3. These are chosen at random, which will be changed before the final version is released. I'll instead, set up a table that he cycles through. (Though I will have something set up that will skip or reset the table to keep it from being a set sequence every cycle.) I'm somewhat okay with that random element, given what it is, but in an encounter like Death, I'd like everything to be consistent.
Another random element to Death are where the single spawning scythes appear. They always appear at the top of the screen, with a variance of 16 pixels along the y. For x, they'll appear anywhere randomly within a 32 pixel margin border of the map sides. This will change to always be consistent for the final version. Something like spawning it directly above him, then the next spawn above the player, then the next being the median between the two along x, always near the top of the screen.
The larger scythe summon (where he'd kneel) has always been set in a sequence. The first is on the left, then right, then the top, and it repeats that cycle.
Gate G Boss
I won't be spoiling who/what it is, however the fight has similar elements of the above 2 encounters. I'll be keeping with my current standards of it being 100% deterministic.