I'd take it a step further and say that phabricator should support diffs across commits, similar to github's compare view. An example of compare view in action:
https://github.com/facebook/phabricator/compare/ffeee378101984140d06f2b3891091e27db5bf58...9be4df02c230bd75edf3037403a6d7c2d3fec1e6