I have noticed that diamond generation has been lowered in someway.

I don't know if this is because of the caves and cliffs update, but I haven't been able to find hardly any diamonds. I have spent 25+ hours on this world, and 5+ hours mining on Y11 & 12 and I have found 2 diamonds total. I tried strip mining, caving, everything, but nothing seems to work.

I even mined two full chunks in survival to see if I was just mining wrong and still no diamond generation! 

I doubt at this point that this is down to luck. I've tried every trick in the book.