Dashboard does not have hard-limit for number of courses - Performance issue

Dashboard (block_myoverview) has cosmetic course limits via javascript. It, basically, loads all courses, activities, notifications etc in one go, and then they are hidden and toggled via paging/tabs. This causes huge performance dip when the user has more than 20 courses (in our case, some originally had 260+ courses and now 110+). Configuring cache for fast mod info by raising it beyond 10 becomes useless once the cache is huge and has an adverse side effect.

Dashboard limits should be hard, and when navigating/paging, an xhr (similar to getnavbranch.php) should be added so to call on-demand rather than loading all in one page.