Shattered Kingdoms

How about this?
By casting voodoo the shaman opens a connection with his victim. The ritual is long and known to exhaust even the sturdiest of the craft. The caster upon maintaining this link can send different spirits to torture his victims severing his senses, weakening him even making him ill or poisoned. Should the shaman wish to he can inflict physical damage upon his victim, though that comes with an even greater cost. The shaman loses some of his own health as the ferocious spirits of voodoo make no discrimination between the summoner and the victim. In the end, should the caster be willing to sacrifice his own life he can let the spirits consume them both, killing them.
For the duration of the ritual, and due to the connection between the two, the shaman is acceptable to any portals aimed towards him.

So in short, the shaman can start sending maledictions at first one by one at the cost of mana. Obviously more needed than a normal cast, for as long as the concentration endures, the shaman is open to gates and remains immobile but the moment it is severed he can walk freely.
He can then choose to harm his victim at the cost of his own health as well. That could mean that he can either damage him a little over time or chose to slowly kill him. Both damage and maledictions will be done over time giving the victim time to react. At any point of the process, should the victim gain access to Spirit Aura, the connection is lost.

How about removing the spell entirely, as it doesn't effect a shaman's playability, PK ability, tanking ability, maledict ability, healing ability, or RP ability.

Agreed.

I'd agree to this if they could get a damage spell that could actually hit a demon.