Thankfully, the latest version of the modpack fixes the lack of copper and tin ore in the world. Unfortunately, it's very unbalanced right now - copper is approximately twice as abundant as iron, while tin is almost ten times as rare (tested in several different worlds).
This makes bronze, which already takes several steps (including smelting copper and tin into ingots, crafting the dust and then smelting it again), even more expensive (especially considering the other uses for tin). My suggestion would be to halve the amount of copper ore in the world, make tin about half as abundant as copper, and make the bronze dust recipe give two or three bronze dust instead of the one.