Semi-AFK Instant Respawn Experience Farm 60-80 (Patreon)

Although there are many NPC battles taking place constantly in warcraft, generally speaking players cannot piggyback kills for experience grinding as there are usually countermeasures in place 1) The mobs do not actually do any damage to each other at all or 2) any damage to a mob by an npc is subtracted in % terms for the xp you gain from killing the mob.

The friendly mobs at the following location are an exception: they do decent damage and provided you get the first hit in, the hostile mobs give full xp. The location is 33,79 Zul'Drak, Northrend, just below "C" in Light's Breach on the map. Friendly Rageclaw Mobs attack Drakuru Trolls. 

This farm is best suited to ranged classes who deliver multiple instant low-damage attacks, though it can be done by all classes.

This is not a super-fast method of leveling, however it is easy to automate.

The trolls also drop a decent amount of Frostweave Cloth.