Don't you think there's too much of ores? I just encountered, I think, two veins of coal together and it gave over a stack of coal. I dug six previously ignored veins below my house and ended up with more than three stacks. That's enough to smelt whole chest of sand/cobble/potatoes. One small trip. When I'm below y40 I simply ignore all the coal to not waste time on something useless. It's similar with redstone. Mere exploring of few caves around y10-20 when I was searching for first three diamonds for pickaxe netted me with whole stack of redstone blocks, probably more than I'll need this month. Iron is even worse, there's no point in creating stone tools because for every iron pickaxe you get 10-30 of iron. Whenever I start new world I have full iron armor and all iron tools before first night ends. Only diamonds and gold mean something but even those are found in big amounts when you start branch mining. I miss the sense of challenge beta provided with smaller and less common veins. Clay was something to be excited in 2011, now it's in every pool bigger than 10x10 in huge amounts.
Honestly, I don't think they've changed the amount of ore there is. You are just better at finding it now. I've noticed that with a lot of people, even myself. I've been playing since early Alpha, and things have definitely changed. One thing that has changed more specifically is it all seems easier... But that might not be true. Maybe I'm just more experienced now.