The best class for WOTLK

Hello there! I'm new to the MMORPG kind of game and just wondering what is the best class for WOTLK?

I've made one account where I'm a hunter and I've reached level 40 with the help of some good people but feel that hunter is not really a good class for me. For anyone wondering what build I use, I use the MM build and also I've been upgrading my gear but still I just feel that there's no damage coming from me.
And because of that, I've been searching for a new class that I can main, preferably an all-rounder class. I really want to help my friends while also giving damage to the enemy.

If you guys can help me that would be wonderful

Paladins and druids can fill all 3 roles - damage, tank and healer. Even if you pick damage you can do some light healing with them if that's what you had in mind under "help my friends". Hunter is good damage when played correctly.
There is no "best" class. A lot of the exceed in specific things and (mostly) all of them are needed later in raids.
If you had top damage in mind - DKs, warriors, rogues, mages all top the charts later in the game.