Its not the exact same thing. Consecration is damage that the paladin is causing. It causes threat from the paladin (lots of it) and generates aggro towards the paladin.

A magma totem is an item that damages something. If your shaman drops a magma totem that damages something, that damage does not generate aggro or threat for the shaman, it damages aggro and/or threat to the totem itself. Although, post 3.0.8 it generates no aggro or threat at all.

So basically its an aggro-less AoE. Also, things like hunter pets and warlock pets that kill something without the master damaging it do not grant XP either.