I think Ezio was developed to annoy. I hate him intensely in opposing parties, especially when doing Crucible of Fire. Why?
First of all: the delay. Ezio, even when about ten levels lower than your own party, dodges over 90% of your attacks. Even when he doesn't do a lot of damage to you, he will still be dodging, itching and scratching for like half a minute after the rest of the opponent's party has long been downed.
Second: he will always come after Jasmin and/or Flora. I tried to make an estimation based on observations. He'll go after Jasmin right away in over 90% of the time, nullifying her effectiveness. This wouldn't be such a big problem, but...
Third: on the Coming Ashore (223) server, far too many people use Ezio in their parties. At some point it struck me: why am I always lined up against Ezio-parties? From then on, I started counting. I have at some point been lined up for 211 consecutive CoF fights against an Ezio party. This was far over three weeks in a row! Come on! For this sole reason, I have withdrawn from this very server. In conjunction with the second reason: I would be generally out of healers by the seventh fight and get no furher than, let's say, fight 10 or so.
Fourth: no matter what people say: there is no true medicine against Ezio. I have tried all strategies I have been reading here, but they will only work for a maximum of two to three consecutive fights. People have suggested Arachna... have they really evaluated its effect? I have compared it to Boomer, but even he is more effective (at lvl 80) against Ezio.
Fifth, at higher levels, a well-equipped (or awaked) Ezio is solely capable of being so lucky as to kill a complete fully enchanted equal level party, without being harmed at all. True, this is not always the case, but he'll give you enough trouble to go and hate the game.