This is the default behavior of resource manager to make transferred data smaller. While this is a hell debugging, it's faster for users to load. Okay, this you already knew. Now, to the point:
Set the resourceManager on your page to format the source. Useful as well -- when you are debugging -- is to set the rest of the scripts formatted as well.
<ext:ResourceManager ID="ResourceManager1" runat="server" ScriptMode="Debug" SourceFormatting="true" />
nicely formats -- and allow your visual studio to actually open -- the dynamic handles without giving you headaches. The ext.axd?v=... handles.
makes the actual source of what you've written using Ext.NET shows nicely as equivalent ExtJS-formated code.
I hope this helps you debug your app.