The way erroneous classes are underlined in Eclipse is much better because it happens immediately. If I delete a class, all the other classes that used the class I deleted are instantly underlined as erroneous. In IntelliJ, I have to wait for a compile to see the error underlines.
If this has something to do with you needing the .class files for proper error underlining then maybe you should add a "compile on save" feature as in Eclipse.
So, what I ask here is the possibility to see the errors right away without needing to make / build the project for that.