Originally Posted by
Endus
That's a reflection of two things; solid class design, and three significantly different roles our specs play.
A pure class like a Hunter or Mage needs a lot of variation between specs to distinguish between them; if a Fire Mage and a Frost Mage both use Fireball and Frostbolt in their rotations, the differences between them start to blur; they're both casters and they both use the same spells. Shaman don't need the same distinction, because each spec is a completely different role; a Healer is going to use spells differently than a melee DPS, who will use them differently than a caster. That role distinction already distinguishes each spec from the other, so we don't need major spec differences to make that distinction even more clear. Instead, as with analogies, the differences we have are highlighted by the shared abilities; each Shaman spec uses Lightning Bolt, but they each use it in a COMPLETELY different way. That helps strengthen the connection between specs, thematically, while they each retain a separate identity reinforced by their role distinctions.
Paladins are a good comparison; they do much the same thing, sharing a lot of abilities and relying on the role distinctions to make the difference. You see this less with, say, Druids, because Druids have the shapeshifting thing, and they tried to make each shapeshift very much separate from the others. As a result, this means each Druid spec feels COMPLETELY different from the others, which isn't necessarily a class strength in my opinion.