Semi-random boss rotation idea

[kyuven]

This is pretty much how a few of the FCOB battles are handled, except in smaller amounts.
In addition, Shiva has a level of randomization as well, though in her case it's a coin flip between sword and staff forms at certain points.
They compensate for adding a random element by cutting down the number of actual mechanics and having the random element be a sequence or target (example: most of t9 has a lot of random elements to it, especially during the, well, elements phase), which makes this less stressful for both the players and the testers. After all, remember that if there are 8 different attacks that can be in any order, that's 64 different permutations you have to test for, whereas if there are only 2-3 different variations based on order and such, you do far less testing and players get far less stressed at having to learn ALL of the mechanics in ANY order. Being on your toes is one thing, but very few players can keep up that level of stress for long periods of time.
Putting the RNG into mechanics layouts as more than a coin flip or 1-in-3 chance also makes certain victories feel less legitimate and losses feel more infuriating. Super high end world first groups would raise unholy hell if they lose a fight and thus the distinction of being "world first" due to RNG mechanics.

[Sylkis]

This is pretty much how a few of the FCOB battles are handled, except in smaller amounts.
In addition, Shiva has a level of randomization as well, though in her case it's a coin flip between sword and staff forms at certain points.

Shiva didn't feel random for me at all, part of it was "Look at me I will show you what my next 8 attacks are" and there seems to be only 1 coin flip on sword/staff, then the other one, then it goes bow (I think).

Coil is the same - a coin flip.

The main difference is that you are given time react to see which one it is then know what ALL their next attacks are, so what ends up happening is that you memorise all the possibilities, which isn't much better. You can get lucky, and only have 1 of them happen all the time (E.g. charge only on T10, tank tether only on T11)

With what I put there, you still have to deal with everything, just in a different order.