You do need both. Some leos need more calcium than others, I have a few who lick at the calcium dish constantly. If it had d3 in it, they'd OD. It's the same thing that every experienced owner will tell you. Without D3 in the tank in a milk cap, with D3 on dusting feeders.
Calcium dishes are a must in the tank, hyposhawn. If you plan on breeding, and DON'T have a calcium dish, you'll end up with weak eggs, and weak mommies from not getting enough pure calcium.