Not quite what happens with Mudras the way you describe it. I have casted suiton, seen the water funnel come up on the screen and TA activate, only to have the server say, oh wait, no you didn't, how about a Raiton instead? Oh wait, you're attacking now, how about bunny instead of that Raiton? Now you get no mudra for another 15 seconds and you have lost a ton of dps.
Also other times where you enter Mudra and the button turns grey for like 3 seconds, preventing you from attacking or pressing any other buttons, because if you do, the server will bunny you because you attacked while it was thinking about what Mudra you entered.
There is also lag with Armor Crush (huton refresh) where if you use it with 1-2 seconds left, the server decides you don't get those 30 extra seconds of Huton, despite the attack connecting and visibly doing damage. Then you watch it disbelief as the last 2 seconds of your Huton ticks away.