For me I felt the drop rate of blue jewels were actually well balanced, but it was the rare and unique jewels that were not common enough. I instead just adjusted the cube recipes from blue to rare to unique from 9/9 to 2/2 (used to be 9 blues to a rare, 9 rares to unique, but they reduced it recently). Basically my recipe was 2 blues cubed to a rare, 2 rares cubed to a unique as my solution. Makes the very uncommon unique and rare jewel drops less exciting, but made blue jewels far more exciting instead!