The reasoning behind one totem per element is that Blizzard didn't want you to be able to use 2 similar aura buffs at the same time. Similar to Paladin aura buffs. You had to choose between Stoneskin totem, or Strength of Earth totem.
Those buffs are gone now, so the reasoning behind that limit is gone. There's really no logical reason for that limit to remain in place except to add perceived depth to the class. Just like Shocks being on shared CDs. Other classes get revampled, or get resource systems, Shaman get to keep Vanilla design philosophies.