Clearly you never played launch with the hillarious caster staves with strength.
Erm, warriors can/could use staffs and priests were intended to be able to mellee... The priest thing later got cut and the staff was probably a remnant of that... Dont see how this compares to a one class being ASSIGNED loot useable only by a totally DIFFERENT class but ok...
Don't forget the quest rewards (Horde side) that had Spirit plate armor.... Still among my favorite was the lack of a skill tree for Hunters at launch. WoW eventually ironed things out and continued to iron things out just as this game will.
Spirit does/did increase HP regen, just because players decided it wasnt a valid stat to look into doesnt mean it wasnt considered to be... Again i dont see how something as optional as a quest reward compares to people being assigned loot only usuable (like, cannot even equip) by another class.
Lol at people trying to justify the terrible state of this game by bagging out vanilla WoW like it was this bad. Please. Vanilla WoW may not have been bug free but atleast it had functioning core mechanics.