During the Halloween event, A friend of mine caught a conversation in Nolani Acadamy where people were saying that Mesmers couldn't get GMC titles. (they were corrected!) That's an example of the typical ignorance the general GW PvE community has towards Mesmers. The cause of this is the "Mesmers suck in PvE" garbage that has gotten spewed out over the past couple years on forums like this one.
It's nice to see that this thread, aside from the occasional silly remark about SS > Empathy (well, duh! SS
is the elite form of Empathy! They had to give it to Necros way back in the beginning because without it, Necros would have only had 14 elites & Mesmers would have had 16) to defend the anti-Mesmer position, has actually had some decent and somewhat valid points to it.
I think that one place that Mesmers excell over most professions is multiple target attacking (I'm not talking about AoE here and Curse Necros may [IDK] do as well). During the initial engagement of a battle, I can get 3 enemies doing damage to themselves rather quickly (echo + Backfire and/or Empathy -depending on mob make-up) and partially shut down a fouth with a couple of well-timed interrupts (usually an Ele or necro, since many of their skills take time to cast) on top of that, I can get a nice little AoE spike off, too. (Cry of pain!) I use this generic bar when out and about in the usual areas. I can adjust it a bit for special circumstances:
[skill]Echo[/skill][skill]Backfire[/skill][skill]Empathy[/skill][skill]Cry of pain[/skill][skill]Energy Tap[/skill][skill]Power Drain[/skill][skill]Leech Signet[/skill]+ whatever.
It's a little bit power hungry, but I usually have Eve along for a battery. This build works very, very well against Margonites using LB gaze and a reasonable LB rank.

The key is to know your enemy and the best way to use the skills against them as a group.