But that's were you have the option to use a mez that does not have a blur component on it. There are single target and multi target mez spells with the blur, and with out the blur, pick which ever one works for your situation.
I just have to say, if there are 7 mobs in your target window and you ae mez and one disappears.. it's mezzed and mem blurred. You know it's there, just AE tash(reaggro) or wait to ae mez it again.