There is no question that SMN is one of the better classes at the moment, it offers utility, damage, cc and rez; would I go as far as saying double smn party is unbeatable or overpowered ?
No not really, the fact is pvp is still new, people have not tested all the possibilities, or even unlocked the pvp skills. The off gcd pvp attacks offer a great way of bursting someone down, if you are able to initiate the attack first, something meele dps does better then ranged dps.
I would also argue that there are plenty of pvp resistances that people can take in order to prevent the excess amount of cc, also the difference in gear between certain players is too vast, and could make it even more frustrating when you are fighting a class that is already somewhat of a counter to your own
Bottom line is, Summoner is strong, but its also unfair to call something "OP" before you explore all the other different possibilities it would be best to reserve your judgment until a couple of weeks have passed