And... back to my mesmer
They are strong in the sense they have the luxury of the “set up” or ambush… If and only if they can summon their phantasms. Blind if in range of the mesmer and dodging are the easiest remedies. In SPvP they are insane to deal with 1v1 but the phantasms are too squishy to deal with pressure from an secondary target. That’s why they excel at the 1v1 they have no pressure because you may already be on the defensive.
Playing against that type of mesmer has been difficult and requires practice in reading the enemy mesmer. You have to be absolutely prepared for that moment when you see that GS Mesmer’s hand go up. You also have to be absolutely prepared to make a counter attack that puts that enemy mesmer immediately on the defensive…
Remember phantasm based Mesmers have 3 defensive strategies from the most general stand point of course and that is (Stealth, Distance and Burst).
Your main objective is to gap close and utilize your terrain/environment. Sometimes it is advantageous to distance your self from the Izerker other times you need to bring it in close. If the enemy Mesmer is glass so is the phantasms in that case try to kite the phantasm by being familiar with its attack intervals…so you can possible destroy it along with attacking the Mesmer.
Honestly at this point most people say Phantasms build are OP. Why? it requires the least amount of effort offensively by the Phantasm Mesmer but the most effort from the opposing enemy to counter by apply enough pressure to that Mesmer to create and advantage. This advantage can only be created by paying attention to many details…
That is why you will see Mesmer’s retort that phantasms are not cut out to be what people make them outside certain places in the game(SPvP/ 1v1 Duels). Once you get used to seeing those details and limitations you can put the needed pressure on that Phantasm Mesmer and hopefully find the opening you need.