Not pointless 3.0 nostalgia.
Healers either need a potency down, or a mp cost up. Currently both are way too strong, especially in concert. Ideally healers should probably be less about direct heals and more about support or buffing, as healing in general in pvp is wearying even when OP and is more like tanking.
DPS need more defensive abilties to compensate. They are made out of paper, and often are the weak point in a match. Both individual abilities and group abilities are needed, the latter to balance out the roles a bit more. Or possibly, boosting attack when in concert. Currently DPS is just focusing a target and trying to get them to zero, with very little additional play. CC might be effective to distinguish them, but its hard to combine it with both dps stacking and high damage single abilities.
Tanks...well tanks are less about protecting, and more about being chunkier dps. I'm not qualified to speak much on them because I dislike the tank class in this game; it's essentially a dps class that uses cooldowns to soak damage. They are hard to balance in general.
We have two modes in game, small party competitive and large party casual. Feast/Frontlines.
-Feast in general is ok in structure, but suffers because healing takes far more responsibility and skill than the other classes. That is, healers have outsized impact on a match. They also tend to be the least numerous role, because healers in general tend to be carebear. I mean, you support the group. I think that they have to be nerfed, and responsibility spread out to all the other roles. Tanks should heal or shield more, DPS should cooldown or peel more. Currently its often 3v1 on both sides. Maybe ideally make it so that you can run without an actual healer instead; that is what made potd viable, and might speed up queues all around.
-Frontlines is actually decent. the problem is this game's "pvp community" will never treat it as a fun mode. If there is a winning strategy, no matter how cheap (spawn camping in seal rock, stacking one side in shatter, stacking heals in rw, mass cometeor spam in secure) it's going to happen. You are going to have to think of testing from the mindset of a rather nasty player, and look for ways they would break the mode down to achieve wins without hacking or cheating directly. Then its just whether or not its an acceptible loss. Spawn camping in seal rock sucked, but wasn't an ironclad win; the others though influenced much more directly. If its not possible, you may need to deemphasize rewards for wins to a small degree. An achievement that takes 100 wins or 1000 matches played is better than one that takes 100 wins-you still have big incentive to win and get it faster, but you arent frustrated if you constantly lose.