Yeah... this. I just noticed that several people have quoted you on this and I just had to join the tally.
I cannot express how much I actually hate this battle... it is utterly ridiculous and I hate what it does to the party dynamic. I've even seen highly skilled players fail this stupid crap several times and like I said before, its far gotten to a point where it needs to be an isolated solo trial. Your play, your skill, your lag, your trial... solo.
Either that or they need to have an extra 1 second delay placed on his abilities because those puddles are just full of it, lag or no lag... this has been argued several several several times before.
Simply applying the echo buff is not the only solution the Devs should be considering... and the more that newer players approach this stage of the game, the more there will be an ensuing bottleneck on it... and eventually it could make them seek another game.