Hmmm, tough one to decide about 'worst' class.
I play a hunter, 60 with 6/8 tier 2 and in PvP I can pretty much 'pwn' all. However, it depends on the player behind the character. For example;A good warrior will not let a hunter get 8 yards away. A good rogue will try to pick you off when your alone, stun-locking you to death.
In my 18 months of playing Ive seen some really crappy players in awesome gear be out done by the 'n00b' in blues and greens.
However, I will say Hunters are the most UNBALANCED class. With scaling issues occuring mid BWL level, lack of 1-hander weapons thats NOT taken by rogues/warriors, lack of 2-hander weapons thats NOT taken by warriors, poor itemisation with ranged weapons, the 10 second rotation to get best DPS, only 3 avalible specs (yet only 1 will get you into raids), being the butt of all the jokes, blamed for every wipe (with your pet got agro, even though it was someone else), being a tranq-bot, etc. The list goes on.
However, I am looking forward to TBC. Most/all of the issues i have with the Hunter class should be fixed/tweaked.
The one class that isnt broken is Warriors.
Just spec to fury, life is soo easy then. Or be a tank.