Our company want to certificate emploees knowledge and for this reason created several surveys (about 10). The task is to collect data from this surveys and determine how much correct answers each users have. At first i was thinking about workflow, which collect users answers (only correct one) from all surveys and store in separate list. But the problem is that sharepoint can't export to excel filtered list and create view for individual user is not possible, because there be more than 8000 users (our company is chain-store). And now i have some doubts will it be a good user experience for survey administrator to filter list for more than 1.2kk items to validate user knowledge (8000 users, 10 surveys, more than 15 questions each). Maybe you can suggest some good approach to collect data across multiple surveys, like using SSRS or develop custom web part to display all results for certain user, or maybe some OOtB feature will be useful? We are using SharePoint 2013 Enterprise
Combining the lists may be best achieved using SSIS. Once you have a single data source you can access the list from Excel and design a dashboard in Excel and deploy it to SharePoint. Alternatively you could use PowerView to create a dashboard. You should also consider using PowerBI which would suit any 'power' users.
Figure out how to combine the data first, and test it, Then design the UI. You'll need Excel Services running on your SharePoint instance to get a nice interactive experience. Use PowerPivot in your Excel Workbook for the data, and use slicers and suchlike to filter and give a nice UX.
The advantage of using Excel is that you can empower your users to create their own interactive reports. SSRS would take not give the same interactive UX. Once you have the Power Pivot Workbook loaded it can also be used as a report source for SSRS.
I can't remember, but you may need Pivot Table services running in Share Point as well. There are quite a few options here, this is just one approach. Have fun!