The only fights I can recall off of the top of my head that you had to move before the markers were Scathach and Calofisteri. Both televised their moves if you watched their bodies and televised what directions for a good 6 seconds before doing the attack with the ground markers going off for a split second and doing damage. Other than that, can literally think of no fights that do that. I can't think of a fight where mechanics happen sooner than 3 seconds apart. They might have resolutions that happen and visually happen, but that's once the game already knows you're dead. They also use animations to hide some of the way the game displays on your end to hide some of this.
To this day, I still see people jump out of AoEs while trying to explain to them that jumping hinders you. The game doesn't update your position until you land. The same people that often say, "but I was out of it." Yeah. You were. If you had run out. You were in the air that time, so you were still in the AoE.
Yes, FFXIV does run on a 3 second server tick. All you need to do to see the server tick is watch your MP bar, TP bar, or HoTs/ DoTs. From one tick to the next, you will count 3 seconds. There are add-ons that actively track the server tick (so BLMs specifically know when their MP regens will hit and can go back into Astral Fire ASAP). For Bane and Sidewinder, it's always been advised to wait a skill in between (you CAN use it sooner, but you run into the risk of not getting the full effect). These also do not rely on the server tick for the game to recognize they are up on the boss. However, do notice they are skills that are oGCDs- skills you can easily hit before even 1 second has elapsed.
Here's something to think on: why are most skills in durations of 3? Regen: 21s; Asylum: 24s; Medica II regen: 30s; Aero III: 24s; Aero II: 18s; Lucid Dreaming: 21s; Thin Air: 12s; Cleric Stance: 15s; Leylines: 30s; Sharpcast: 15s; Thunder 4: 18s/12s; Goad: 30s; Higanbana: 60s; Miasma: 24s; Bio II: 30s; Adloquium+Succor: 30s; Shadow Flare: 15s; Miasma II: 12s; Excog: 45s; cards: 30s. Ugh. Tired of typing these lol. There are exceptions, which I found most to be straight buffs (like healing potency up, effect extentions, stuns) as well as being oGCD. All over time effects are effectively snapshots of what buffs/debuffs you had going and are kept that way until you are forced to refresh them. Also, because of the server tick being 3 seconds, this is why you do not refresh your DoTs before 3 seconds as it is a DPS loss. Recasting, say, Ironjaw when both DoTs are at 4 seconds means you might be losing a whole tick of damage (possibly 2) because of the server tick. There are tons of guides on this, especially in Bard and Summoner ones.
Yeah, having fast actions can definitely make this game frustrating at first. Then you realize you don't need fast reactions to do most things in this game. It's very inclusive. The slower server tick is, oddly enough, meant to make the game easier to play and it actually does. The people that actually suffer are the ones with slower reaction speeds.
The reason I "defend" it is because instead of complaining about a change that may never happen, I learn to adapt to it and take consequences into consideration. I've had an LB kill me once- was a healer LB 3 in Ramuh EX and we learned very quickly there is no saving you in Ramuh EX. If they removed the recovery time, that's cool. That's a nice improvement. It still won't help healers that pop LB3 in Sophia EX during her tilt mechanic and res the entire party into sliding off (had that happen so many times) or fights where they just pick horrible times to LB. Until then, I'm simply just not going complain about it and learn to work with it. Personally, I don't see people withholding LB unless it's a monk and they are the only melee- understandable since the loss of GL hurts them horribly.
I mean, your complaints come across to me the same way people have complained about not being able to heal constantly in monster hunter. It's a design choice. You have every right to complain, just like I have every right to say I think you're silly. You have your opinion; I have mine. However, the thread wasn't about how people felt about LB animation locks, but asking how long, preferrable by frame, it took for each job to cast, execute and recover from LB and see if there was an optimal job to use it. I highly encourage you to make your own thread on that topic.
¯\_(ツ)_/¯