I plan on getting 89 herblore for super antifires and to use Zamorakian spear for Iron/Steel/Miths etc but would zspear also be the best choice for blue and black dragons?

Abyssal whip is best for all dragons but mithril and KBD. Irons and steels are better with whip/defender than z spear, and so are black and blue dragons.

Abyssal whip is best for all dragons but mithril and KBD. Irons and steels are better with whip/defender than z spear, and so are black and blue dragons.

Are you sure? I got to 135 steel dragons/hour last task with zs (with spec restores and claws though), so whip would have to be really good to be better.

Not sure about irons but both I'd say zs is better for both steels and blacks.