There is an up to .5 deduction for pike, in all three phases of the vault.
We have an up to 1.0 deduction for the angle of repulsion (so where your body is when you do block off the vault) and an up to .3 deduction for being on the vault for too long. Block also ties into height and distance, which are up to .5 and .3 respectively AND dynamics, which is an up to .3. (I don't have my book with me, so these are coming from memory and I'm not the most amazing vault judge in the world, so if someone else knows differently, then I'm probably just getting some numbers confused.)
In my experience piking and lack of blocking often originate in the hurdle and body position on the board. I'm sure there are some very knowledgable coaches here who can give a little more insight into this.