Guild Wars 2

Dueling was once a key specialization, primarily for deceptive evasion, had good synergy with chaoss (desperate decoy with prismatic understanding) and illusion (blinding dissipation and ineptitude).
At the moment do not find space in any competitive build, primarily because it not help good defensively (as does insiration) and even in attack (as does illusions) and deceptive illusions has been replaced now illusionary reverse and chronophantasma.
The amazing thing is that dueling has valid traits such as mistrust, deceptive evasion and harmonious mantras, the problem is that as most experts mesmer, are all three in the same compartment.
Guess what would suggest doing? ^^
Put deceptive evasion instead of evasive mirror.
In its place in the grandmaster department a new trait, there is someone who uses evasive mirror?
In any case I think that if only this change could make it more interesting specialization.

Duelling is being used in Mistrust builds

Dueling/Illusions/Chrono

or

Dueling/Chaos/Chrono

Having said that, yes, moving DE to Master would be a smart move, to make it more appealing for Chrono setups (hybrid and power) and help vanilla mesmer.

Moving DE to Master has been a suggestion since forever. ANet clearly wants it to be a GM trait, for whatever reason.