My Mesmer is 37 and honestly the class "feels" like it has to work twice as hard to perform as well as a Warrior (for example). Survivability is not an issue I've found, as using Blink and/or Decoy provide excellent escapes. Damage is not bad either. I've found using a Greatsword / Staff combo works well providing good defensive, AoE, and damage output.
Now, from a maxed out PvP standpoint my Mesmer is a monster truck...Mesmasaurous or something. I feel near impossible to kill unless I get swarmed by enemies. 1v1 I rarely lose except from those hilarious 1-shot glass cannon builds. So the class is good and inherently has some tankiness due to the clones/phantasms.
One other thing I might mention is to look on the Trade House for level appropriate Green (next step above Blue) quality gear. I re-geared myself from questing Blues and it did make a HUGE difference. I am back to being able to be somewhat lazy and not have to weapon swap 3 times every fight.