From my observations, the game uses some kind of universal hidden "round" system. Think of it as WoW's Global Cooldown: Even if you have TP and stamina, you just cannot spam 3 WS instantly; they'll all occur about 1 second after each other.
If you already did an action during one of those "rounds", the game won't let you act until the next one. Because of this system, it can be pretty hard to get both Haymaker and Jarring Strike to register after an Evade. (You have 2 "rounds" window to use feint or counters, so usually if you have some input buffered in the queue, you won't be able to get even one ability out before the window closes.)
This is also why you can't burn your entire stamina on light strikes/flurries and what-have-you in a second, but need a couple of moments to do so. This totally can give the impression of lag.
If you act "late" in a round, you can sometime get 2 moves to fire off seemingly instantly one after the other, but never 3, because you'll have to wait one complete "cycle" for the next one.
Rogues in world of warcraft used to have a universal timer on their energy regeneration, which was, iirc, 20 points every 2 seconds. People started using mods that would warn them of the arriving "tick" of +20 energy, and they would learn to burst fire right before the regen, so they would effectively gain an advantage in DPS, especially in PvP after opening from stealth.
This was all "ruined" when Blizzard started to give 1 energy every .1 second, effectively killing the extra 20 energy "pro" players would use.
I've mentioned the above history lesson just to show that it's not that weird from square to use a system like that -- Blizzard, that are often pionneers in mmo technology, used one for a couple of years on their own.
It took also a couple of years to perfect their network code to allow for 1 second GCDs instead of the 1.5seconds that was enforced at the beginning.
Hopefully, we can expect Square to follow and upgrade FFXIV in a similar fashion over the next few years (although I'd prefer more content than system upgrades at this point...)
Edited, May 25th 2011 7:57pm by Docent42
agree with FFXIV observations , is more fustrating for "buffs" ,i can chain a Tp skill with a built tp skill actually . but yeah....
however disagree with WoW rogue , i prefer the new energy system (ISNT 1 energy/ 1 sec lol , more like 1 energy 0.1s) , is streamlined , no "tick", and haste = energy regens faster ........is awesome (for me ) , yeah a timed "tick" is free 20 energy but......having 50 energy and want to MUTI? wait for energy tick! bleh :P
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