I think all classes are very well balanced here and every one is needed.
Shaman
+ awesome buffs
+ awesome mana re-gaining
+ ok healing
+ best resist debuffs
+ different types of slowing
+ only class with epic currently in game, which makes them the best slowers if they finish it
- will get pestered for buffs
- no group heals
Druid
+ good healer
+ has some nice buffs
+ group ports to lots of places + succor
+ can do some dps
+ can kite well
+ tracking, foraging
+ damage shield
- will get asked for ports a lot
- at 65 the pet is almost useless
- root spells do damage
Rogue
+ nice dps
+ can scout around
+ lockpick!
- low survivability
- doesn't have the "gate" spell

- hard to solo with
Shadow Knight
+ best aggro
+ FD
+ good tank/splitter
- I see nothing bad about them, my favourite tanks.
Well, maybe the fact that melees and hybrids are more dependant on gear than casters.
Beastlord
+ good pet
+ can tank to some extent and does some dps
+ some nice buffs, especially casters love them for wrath/cunning <3
Mages <3
+ awesome pets, that can be offtanks in groups if needed
+ even better AAs that affect their pet
+ nice toys to summon
+ damage shield
+ good dps
+ call of the hero
- are less dps on mobs that whirlwind (because most of us try to keep the pets alive)
- almost cry when they see their fellow mates wizards do primal blasts