A Goblin Shaman's spells are weedy and irritating, but dangerous - just like Goblins themselves. While Orc Shamans tend to be seen as trance-addled buffoons, Goblin Shamans are cagey and cunning, if no less odd. They often use their magic to barter for tribal influence. Many Goblin Shamans work their way into a top position, either directly advising the Warboss or even taking the command role themselves. Any Greenskin that opposes a Goblin Shaman is apt to suffer nasty rashes, mysterious beetle infestations or some other wicked malady. In battle, Goblin Shamans turn their spiteful spells towards slaying, or at least annoying, the foe. These spells are more subtle than their larger kin's, but no less effective. When an enemy fails to charge because they have doubled up with itchy hives, or the weapons of the Greenskins seem to dart unerringly for weak spots in a foe's armour, it is often due to the magic of a Goblin Shaman.
The Goblin Great Shaman provides a Lord level caster to the Greenskins. The lore of the little Waaagh provides many annoying debuffs to enemies and helpful buffs to allies. The spell, Vindictive Glare also allows him to work down enemy large units from a distance. From a multiplayer perspective, Greenskin lords are almost always targeted and killed. This Goblin on a wolf is one of the fastest units in the game, meaning that it can outrun most things that chase it. While this does not guarantee he will survive, he has very low melee stats and health, it does prolong it and makes sure that your opponent has to invest a lot of micro into killing him. He is also cheap compared to Azhag or Wurrzag, meaning that the rest of the Greenskin army will be stronger.
The Catchweb Spidershrine mount makes the Goblin into a tanky and damage dealing caster. With 7,000 health and 120 armour he can survive where most Greenskins Lords would fall.