Mesmer can’t stand in the current meta not because they are bad , just thief can do a better job on dealing dmg and roaming.
My suggestion is to remove Deceptive Evasion and build it into mesmer’s basic mechanic. This trait is such a failure that force all the mesmers to waste 4 points on dueling. The original Deceptive Evasion could be changed to something like “increase x% dmg against the target who has higher armor than you,” maybe like [target armor – your armor]%? This change could also gives mesmers a more specific role in the game, which now the thief cannot easily replace.