See video made by de.wp user:Gnom: https://www.youtube.com/watch?v=Dm_WyFfMC1M
"Trying to mark a big chunk of text in a Wikipedia article using Visual Editor, first with the shift and arrow keys, then with the mouse and a trackwheel, then with both combined. Windows 7 HP SP 1, Chrome 38.0.2125.122 m, Vector, 17 November 2014."
I tested quickly with Chrome and FF.
On the first one, while pressing Shift + arrow down, the selection works until I get to the last line I'm seeing on my screen, but the view doesn't scroll further down, so the action might still be working, but I just am not able to know it. (Shift + arrow up, from the bottom of the page, seems to work better instead).
But, depending on the speed you hit Down, it might lose some of the selection.
On FF instead instead the selection just stops working after the 3rd time or so you click on the up or down arrows.
In both the browsers, clicking at the beginning of the article, holding Shift, then scrolling all the way down to the end dragging the right scrollbar with the mouse and clicking again after the last word at the bottom worked just fine (also the other way around, from bottom to top).
I wouldn't know about other combinations such as Shift + Page Up/Down because I'm not entirely show of what should be the expected outcome there.