I'd like to say before I give my serious opinion that the results of this poll show once again that there should be a selective group on these forums that have the right to vote. It's pointless to have polls when the results show no correlation with reality. I am pro free speech but rather a serious poll than a trash poll.
My post is built up in sections to give a good overview of how I feel about 19's balance. 2 main sections being arena and WSG with subsections healing, CC, burst, survivability and FCing in WSG.
Healing
Arena
We can definitely say paladins are most underpowered here. They have no instant heals or HoTs of any kind. Druids and shamans are on par because they both have amazing CC to avoid being interrupted. Priests are better than paladins here because of their renew ability and their psychic scream, but they have more serious mana issues and don't have a travel form or spirit wolf like druids and shamans.
WSG
Pretty much the same applies here, though druids beat shamans because of their ability to shapeshift out of polymorphs and priests (however still behind shamans) are slightly better here because they have instant HoTs for mass healing and they can shield their FC when he's under pressure.
Crowd Control
Arena
Mages are king here. With the ability to slow opponents up to 9 seconds with a mortal strike effect on top of that and frost nova as a mass CC ability when under pressure they have perfect control over melee classes and combined with polymorph they can annoy healer classes to no end. When they /spit you know you're doing it right! Most underpowered in this area are paladins. With a 3 second stun (5 when talented) every 1 minute we can definitely say paladins have the hardest time catching up with opponents. They have no sprint or travel form or any kind of slow ability to keep targets in melee range and they don't have stealth or charge like the other 2 melee classes, making it nearly impossible to get a good opener too. Rogues have the most amazing CC ability at close range, with gouge having a 10 second CD they can make sure slow healing classes never pull off a heal when combined with kick.
WSG
Again, nothing beats a mage. They can make or break a pug aswell as a premade. Besides that it's basically paladins that are the losers here, again. Their hand of freedom is one of the best counters in the 19 bracket though and this is where rogues and even more warriors lack ability to catch up when they are kept in combat. All other classes are pretty well-balanced, with shamans and hunters being very annoying in 1v1 situations but not rediculously overpowered at this point.
Burst
Arena
This is the only thing paladins really stand out on. A paladin that knows how to play can take you from no worries to death in just seconds. Combined with their hammer of justice an isolated prey can easily become powerless against a bursting paladin. Druids are rediculously underpowered at this point, with wrath + starfire being their best burst potential with a mere 300 damage max in SP gear this class can't surprise you. With the exception of fire mages bursting 500-600 on occasion the other classes have more sustained damage with some small burst potential. Of course there's the rare ambush/backstab rogue but they generally lose any viability after 2 seconds of breaking stealth and they rely on poorly geared clothies and crit chances to win.
WSG
Same applies, though in pugs with significantly less healers and overall more poorly geared players ambush/backstab rogues gain some viability.
Survivability
Arena
Survivability is one of the few things that is quite balanced in 19 arenas. Cloth-wearers have enough abilities to make up for their lack of armor and classes with heavy armor will lose a lot of health to chasing their opponents to make up for the larger health pools most paladins and warriors have.
WSG
With terrain being a huge thing in WSG melee classes will find themselves underpowered on survivability. Jumps are in a caster's advantage almost always.
Flag Carrying
WSG
Sadly, shamans and druids are overpowered to a point where all other classes are said to not be viable. This is not entirely true as good CC skills can turn any class into a viable FC, but I do have to agree that travel/wolf forms make shamans and druids the best option for both a pug and a premade. Druids being slightly better in pugs with their ability to HoT themselves and shamans being better in premades because of their mana efficiency and because they take less hinder from slows.
Overall I can say paladins are the most underpowered class while shamans are the most overpowered class, but that this opinion is based on overall info. The balance depends on situation.