Leather armour can be used by all classes except mages,warlocks and priests. There are two types of leather armour:
1. Agility, stamina armour: best for feral combat druids and rouges, also good for hunters, ok for warriors, paladins (retribution, protection) or Death knights, even though they dont give strength and good armour.
2. Intellect, stamina armour: best for restoration/balance druids, good for shamans (restoration and elemental) and ok for holy paladins.