Thank you for your feedback.
Actually the MVC used is Sitefinity is implemented as a part of the WebForms. Thus you have ability to use for example multiple MVC widgets on Page. In its implementation Sitefinity looking for the Views in the standard views folders Views/Controlle
r and Shared
In other words it is the expected behaviour not to find the Views placed in other folder/s except in case custom registration as you already mentioned in your initial post.
Note that the Views in Sitefinity could be under (~/MVC/Views) or directly in the root (~/Views).
In addition, we have test the view in a sub-folder of Shared folder on Standard MVC 4 application (attached) and the view is also not found without custom path registration discussed above.
Alternatively you can use Sitefinity Feather. Samples of custom MVC widgets with Feather could be found here and here.
I hope the information above was useful.
Your feedback and the shared solution provided are appreciated.
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