Diamonds are harder to find???

Since the 1.3.1 version of minecraft came up, I started to force update my Minecraft. I created a world and started playing and exploring new things, I am mining more than 3 hours and didn't find any diamonds. When I gave up Mining, I opened my X-Ray Texture pack ( I knew it was cheating ) and played again. When I came to my mining area, I didn't find that much diamonds, Most of the diamonds are near the lava pools. So I find only 23 Diamonds using The X-ray Texture pack. What does this mean? Is the diamonds really harder to find? or it's just only my map seed. I went to Minecraft wiki and searched for diamond, when i got there, I didn't find any changes in rarity of diamond, Please help.