I must say that both ideas in the poll seem good to me, so I voted for lower the cost. Why? Because I realised that this+catapult is awesome (not OP), so it doesn't need any more stuff.
Even though, making it target the player allows some other good stuff, but I think it should be changed of element, for synergies sake (plague and this are in the same element, and meh, doesn't buff duos). Maybe light/water/gravity can fit this too.