Unfortunatley the behavior of the client and the webview (and the vSphere web client) is not the same. I think at first this was because the client was full featured whereas the web view was limited and needed some optimization. I am not aware of any properties to force to calculate fields per step in the client.
There are a few things that can help speed things up. For example the first line of your actions used for the presentation should return null if they are passed null inputs. This happens if a field depends from another one when you first start the workflow or when you enter information in one field but other required fields are not set yet.
There are other things that can be done depending on your use case but basically limiting the field dependency, only calculating fields when needed.
Christophe.