Shovels with Efficiency Enchants are not digging blocks correctly.

What I expected to happen was...:
The blocks to dig/mine really fast.

What actually happened was...:
The block(s) would break after 5-10 destroys.

Steps to Reproduce:
1. Enchant any kind of shovel with any level of efficiency.
2. Mine any block. (Like dirt).
3. Begin digging/mining. It wont work correctly.