The problem is, it's still "Every chunk looks basically the same". Every chunk has so many plops of a given ore. Those are not veins.
Veins ... imagine an iron vein that is 1-2 blocks wide, 60 blocks long, running into a D=7 ball with two more veins running off of it. And that's an average size one. 100-120 blocks in length from end to end. Not common, but if you explore caves or ravines, you'll see a block or two of exposed iron, and then you just follow it.
Vanilla style plops (needs a better name) are basically "Dig anywhere, it's there". Even reducing things to one larger plop per chunk still means "Just dig around".
Something that shows up about once every 25-75 chunks, that has to be found by intelligent looking? Your clues are:
1. Most likely in a small vertical range,
2. Most likely in a frozen biome
Up through 1.6.4, that was good enough.
A COG cloud is ... very, very rare. The main cloud itself might be spread across 8-12 chunks (D=3 to D=4, roughly); "hint" singletons can be found for a radius of about 100 or so blocks. You find the hints while exploring, and use that to try to find the core. These might be every 250-400 chunks.
(TFC: The Full Conversion mod?