there are a multitude of issues surrounding many classes, some people will nitpick on classes they dislike for players they dislike. having played all classes to a considerable degree, i believe there are some skills worth focusing on before moving on to minor and less problematic issues.
twins: one of the biggest issues surrounding them in pvp is their ability to weave and power weave within a very short duration. this allows them to escape virtually any and all attacks while still being able to attack enemies with their twin counterpart. they are especially resistant to DoT's and status inflicting skills that are activated upon inflicting damage (blizzard is an example).
so in short: lengthen weave and power weave cooldowns by 2-5 seconds which would limit weave and power weave being used in tandem.
summoners: their damage reflect is a major cause of concern. this will instantaneously kill certain classes. many end game summoners do not use it since it is genuinely broken.
invoker: an increase in magnet duration is necessary. 3 seconds is a good balance of the awakening and mp cost.
things to remember:
client sided issues cannot be resolved due to players varying internet connections. there will always be laggers.
x spamming isn't the issue. people who choose not to farm elements and then complain about elements being held for those that do farm is an issue.
players making suggestions for classes that they have virtually no experience in is an issue.
there is no nerf for a player's ability in pvp. skilled players will win.
resistance overpowers element attacks with POS. invokers get nerfed since their x spam is reduced by 70% in all pvp modes. against pos and decent resistance cards, their element damage in pvp is laughable.
they cannot compete in terms of physical attacking classes in terms of stacking element damage. increasing cooldowns on a ground locked class is debatable, especially when people are also requesting x spam nerfs and heal nerfs. are you expecting the class to run around with no way of fighting and taking hits to depreciate their armor durability? hilarious.
invokers are not difficult to play, but they are extremely difficult to master.
summoners x spam requires a lot of attack speed stacking. they are forced to remain stationary, being susceptible to attacks and DoTs.
healing in pvp does need a rework. however, any class at this point has the ability to be immortal. stacking resistance with pos + high hp, any class can capsule and cake.