You know what I would like to see more of, are encounters where even if you know the mechanic coming up you don't necessarily know the exact AoE pattern you'll have to deal with. Some of the Nier fights are great examples of this, where you have to watch the boss animation for tells of where the attack is going to take place. The bosses in Aglaia have some good moments of this too, especially the last battle where the colour of the background denotes which AoE is actually going to occur. I think a lot of people still don't understand how the yellow stack marker versus the blue circles actually works, lol.
Castrum Abania had that boss who changed elemental attunements, so you had to pay attention to which element you had to charge up with yourself or face the consequences. I still saw players who struggled to figure that out, before they completely changed how the boss works that is.
Another thing I'd like to see, and I say this all the damn time, is to rebalance item level scaling so that you can't just ignore mechanics and stand in AoEs all day long. I see it all the time, where someone clearly doesn't know the mechanics and doesn't care, and by the time the fight is over they still don't know and still don't care. And they aren't even new. This goes for dungeons, as well as raids, and yes I mean Crystal Tower as well. Whole mechanics are literally not ever seen anymore because the boss is dying before it can get to the real "tricky" phase. Again, back to Aglaia, if these bosses live long enough they will start to mix things up and give us more difficult variations on their abilities that WILL consistently get people killed, but we never see these phases anymore because players are so overpowered that the boss just melts long before we're even close to that point.
This is also true. It can be fun to showboat and take educated risks during times when you know it's relatively safe to do so. Maybe I won't hard cast Medica II after a raidwide because I know there's not another raidwide coming up right after, and Assize is coming off cooldown soon. Maybe I let the tank take a few extra hits while I take time to Raise somebody, because I know there's not another tankbuster that could happen randomly. Part of being a healer is planning and thinking ahead. I can't do that if I literally have no way of knowing what might be happening in the next few seconds.
By contrast, most first-timers to any given fight have no idea what the boss can do, or what order it will do it in. So, this whole randomized mechanics order system would literally make no difference to them.