While nowhere near as common as Tier 3, Tier 4 Materia are at least obtainable, and have been for quite some time, even with airships returning a lot of them.

Personally, I'm trying to hit 3* craft/control without the Soul of the Crafter and without food. It's doable, though requires very heavy melding. I'm using one i180 piece, the rest are going to be all i170. CP first and foremost, then Control, then whatever room is left over gets some Craftsmanship Materia.