I like how people want these so called random elements in a fight. The truth of the matter is that most of this community couldn't handle them.

Let's look at Mog EX for example. A little bit of a RNG element and people hate the fight. When the fight was new in 2.2, most groups couldn't beat it and of the groups that did beat most barely just scrape through by sear luck.
The same thing happened in 2.3 with Ramuh EX, a little bit of RNG and a lot of people couldn't handle it.
It wasn't until the echo was added to these fight and a set strategy was known that people cleared these fights.

If we had true RNG based fights, where any mechanic can happen at a given time, a far fewer amount of people would be able to clear content. Then we'll be at this again, but people will be complaining about how unfair that is.