Similarly to Alliance’s Paladin, Shaman is a unique class option for Horde. Shaman boasts amazing group utility with its strong buffs through totems. Windfury totem is a must in any raid while Bloodlust in Classic is unique to the Shaman class. Restoration Shamans were considered the best group healers while other specs were also amazing in PvP environment capable of dishing out insane burst damage. Additionally, Shamans were able to wear mail armor, so any piece with spell power on mail set piece was almost certainly yours.
In terms of what the World of Warcraft Classic Best Classes are, Warrior and Priest stand out almost instantly. This is partly due to the fact that Protection Warrior is the only viable Tank Class in WoW Vanilla Patch 1.12. Both the Proc Warrior and Priest are required for Raids and when combined in a PVP setting can be a fierce combo on the battlegrounds.