As with so many design principles, "it depends." I think Storyline's scrolling panel is great for allowing one to explore a large image, instead of having to reduce the size so much it's of no use or having to break the image into multiple graphics.
For text, I generally write in chunks that don't need scrolling, because -- let's face it -- people seem to avoid long pieces of text and don't bother scrolling. Plus, I find it obnoxious if I have to scroll for just one or two extra lines; I'd rather have the text be a bit smaller and with no scrollbar. However, if certain information truly belongs as one big chunk, then, yes, scrolling is appropriate.
Years ago, writing on the topic of web writing, I created this acronym: KISS & TELL. It stands for Keep Intro Short and Simple & Then Expand Length Later. In other words, provide snippets that entice someone to read further. The more they follow a given path, the more interested they are, so the more text you can give them at a time. Of course, for many eLearning courses, they're supposed to read everything. But you can still provide a brief overview to get them ready for a big chunk of content.