Theres no way the wrath will make the other 4 do more additional damage than just dropping a 5th magma totem... if a magma totem conservatively does 600 damage per tick without wrath, and say 650 damage per tick with it (probably not even that much extra), then dropping 1 extra magma would be 600 extra damage per tick, but dropping a wrath instead would be 200 extra damage per tick. Even if wrath raises the damage of magma by double that you're still better off dropping an extra magma