Astral Fire/Umbral Ice timers are actually bad mechanics at a meta level.

[Taranok]

That means that, unless you've planned things out carefully, you might have to place the B way earlier in the sequence than you intended and put another B later, or replace one (or more!) of the last As with a C, and so on. Not only does the order of spells in your astral cycle shuffle around, but the length of your astral cycle can expand or contract in response to changing circumstances, because a timer controls how many good spells as opposed to mediocre spells you can cram in there.

Fun fact, after mathing it out, if you ever have to substitute in a Fire 1 into the level 90 rotation, it costs you 300 potency. 401, technically, but as it's a faster cast the actual impact comes down to about 300.

I think you can literally screw up a sticker (as in, do a 1-2-1-2-3 combo on SAM because you tapped the wrong button) to even approach that level of punishment.

If you have to interrupt a fire 4, it will cost you at least 400 potency. Closer to 900 if you interrupt it closer to the end, because fire 4 is, legitimately, a 958 potency spell (310 * 1.8 * 1.3 * 1.2 * 1.1). To put this into perspective, Midare Setsugeka comes in swinging for about 1118.7 potency. Higanbana is about 1356 potency. The newly buffed Xenoglossy is 1304.

Why is this relevant? Because anyone who thinks timers add anything interesting to the class in terms of challenge really have forgotten just how much of a challenge it is to not interrupt fire 4s, to greed standing in AoEs to greed out a cast to keep the cast time rolling. Because so much of BLM's damage is tied to individual, long spell casts that even interrupting a single one is on the same order of magnitude as screwing up something like Ten-Chi-Jin for Ninja.

In other news, I hate the new BLM AoE rotation as well. Because it bloats out a class with massively overbloated bars and also, simultaneously, is so long that I basically can only use it in one cycle before literally everything is dead. Between it, fouls, flares, and high fire 2s. Even the old one let you cycle several times on mobs.

If there was no timer, but rather an ammo/charge system, you should still be challenged to use your instant casts when movement is required and to use your instant casts of shortening the effective cast times of your slowest, hardest-hitting spells, but you'd never actually have to make tradeoffs or sacrifices in terms of how many of those spells you'd cast at all. You'd always, rather than just hopefully get to cast six F4s and one Despair per cycle.

Also a lot of tricks that feel great to pull off and get away with would simply cease to have relevance. For instance, if I have 4s left on my astral timer and a polyglot proc that's about to overwrite, I'd normally have to either sacrifice the Xeno or the Despair. But, if I have Swift or Triple up, I can do something cute: cast Xeno, activate Swift as my GCD rolls, and then cast Despair with 1 second left on the clock, breathing a huge sigh of relief as I refresh my timer and get both my hardest-hitting spells out. Without a timer, there's no pressure: my Despair is guaranteed, and the only thing I have to worry about is a delay.

To add this in since I do have more to say on this: I'm not asking, and have never asked, for timers to be removed with nothing to fill in the void. There are numerous things the timers accomplish that should be preserved. My question to you on this is: What could be added that maintains this flexibility and additional punishment you like, without having the timers? Because literally every other class in the game can have their rotation interrupted and not need to go through mental gymnastics to recover the rotation. To my mind, it has never even been a core part of the class. Just something I had to suffer through. It never gave me a sense of accomplishment or feel good, because you have to master this aspect just to play the class. This is why the timers are a gatekeeping mechanic and have no actual impact on the ceiling.

So what could be done that accomplishes this playstyle without needing to cripple the rotation on a complete failure? Because every time someone, including you, defends timers, you assume the challenge cannot be acquired in some other way, or that the class wouldn't get something new. You just assume it will be removed as is. Actually, the part I find most ironic is when people agree with many of the negative things I say, such as dropping timers during boss transitions, but want to save the timers while preventing the drop, when the easier option is removing the timers and doing something else to the class than locking the timers' decay.

Recovery rotations aren't really something I consider a fun part of any class, and the devs seem to agree as they've systematically been nuking every last recovery rotation from the game, Black Mage and Bard being the final holdouts after Ninja, Dragoon, and Monk had their failures removed or, had a button to shore up a mechanic that used to be good, but has since decayed into bad. Bard's recovery being if they die mid-song.