Herald of Plague doesn't function like other Herald Skills

Herald of Plague doesn't function like other herald skills and as such feels significantly less powerful. I feel like it should have the attack tag on it as well so that we can slot the attack skill gems that relate to poison.

As it stands there is no way to buff the poison effect of the skill, which leaves it underbaked. All it does is spread poison, but if you cannot buff the spread from the point of the herald, then theres almost no point in using it.