For starters, We summoners rely more on field control than any other class ( got to pay attention to my cat "buddy" and see if he is fine, manage most of my CC's which the cat is mainly responsible for, health, distance and my defensive CD ).
because we are also built to be a 2 in 1 marshmallow class, the way to fight against any summoner comes to any of 2 ways: CC the hell out of the summoner and burst them down (can't give cats any commands during hard CC) or Kill the cat first (unless it goes into tank stance) then summoner (kill the cat infront of summoner after tank stance wears off). Any of those 2 approach works interchangeably in a duel. Summoner Pwns in low tier pvp but once you figure out how to deal with them it becomes another dead cat gallery. as for other classes its more of a Figure out how they build and play then deal the hurt when the opportunity comes up.
Since we are so easy to kill with the limited 2 option way of approach, we have to manage the full use of the class and understand the build and playstyle of our opponent to ensure victory (usually by annoying the hell out of them and make them make mistakes).
This is what makes us the hard to master class.
So with all said, I don't think its a balance issue in my opinion. Just the mechanic and learning curve of this class.
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