Some courses; like the classic wow gold Hunter and Warlock, gain access to pets which can fulfill the function of a personal tank, vastly increasing the ability to complete quests kills. Melee attacks, like out of a Warrior, can get blocked or miss their mark much more often than you'd like, when leveling 35, causing a divide.
It equates to a divide between the potency of one class over another at a time at which each should be just as capable of beating up simple pursuit mobs. It is definitely possible to make it to level 60 with no support of a buddy or ally that is nearby, but it can feel imbalanced and unfair.
You might as well throw out everything and anything you know about such classes from post Vanilla. A lot changed at some point, as well as playing a warrior isn't as straightforward as it should be. It is good to see the viability of person class builds return, but having existed when they finally added dual-spec, it is painful to return to the dark days before you could fill out the DPS or tank/heal role without dropping a chunk of change for the privilege.
Combat is probably where people playing cheap wow classic gold for the first time will fight to see that the appeal; not since it's complicated or needlessly deep, but because of the way slow and unfulfilling it is by the current standards.