Magick classes only:
Shaman - No one will respect you for winning fights as a Shaman, and isn't earning the esteem of others to fix your lagging self confidence truly the reason you're doing this?
Mage - No one understands mage - even mages don't understand mage. If someone told me that Mage had a skill that gave uncurable impatience, I would believe them.
Runeguard - You're the best knight at afflicting, meaning you're the best class in the game for winning fights over twenty minutes long. Did you read any of the knight vs. knight ToA duels? A few of them were so long I had to clear my buffer twice.
Renegade - People will team you. I'm serious - even coming out of phase you will not get a 1v1. There's apparently this button that your enemies get to make allies magically appear beside them the moment you attack as an assassin, and you're the worst class in the game when teamed.
Berserker - At the end of the day, you're a bard with swords. I know it doesn't feel like it but trust me. Read the bard section because every bit of it applies to you too.
Bard - Your afflictions mean absolutely nothing. You could hit someone with a pillow, and as long as it somehow counted as a 'bard affliction', you would kill them with it. Your affliction attacks are also smart, meaning you could set one of those drinking water birds on your attack macro and win most fights.
Hunter - Hunter is also bard, but they have to actually pick their afflictions instead of the game picking for them. The strategy is exactly the same though, you've just turned the difficulty up a notch for basically the same results. Your affliction pool is also bad, so don't try to play the class like assassin or shaman.
Druid - You will do okay with this class as long as you put a sticky note on your monitor to remind you that it is not an affliction class. You get neat affliction attacks that you should summarily dismiss, and just focus on the fact that your shock/jolt stack hits like a truck.