I'm not a judge... But I think judging more holistically from perfection to absolute slop per phase makes sense. If preflight, block, post flight, amplitude, and landing all start out of 1.0 execution per vault, you just take each phase in turn and judge how good it was out of 10 tenths, max E score is still a ten for both vaults combined. And you can't lose more than a point per phase. I'd think of it as "from 0-10, how good was that phase?" and call it a day. Use the full range from 0-1.0 off per phase, (so you can't lose more than a point per phase).
Examples. Somebody like paseka should be losing .5+ for her pre flight alone. The one armed chengs could get the full blocking point off for not blocking appropriately (and now you don't have an arbitrary 2 point deduction), whereas people like Andrade or Simone are close to deduction free.. twister vaults could be .3-.5, or worse if you're bending your legs ... Little shuffle or lean on landing? .1 off. Step? .2. Chest down and step? .5ish. Roberson drilling a twist into crunched knees? .7. Hand / knee down? .8 off. Can't land it at all? Full point. Just, use the full range of execution as it relates to each phase.