Its kind of hard to figure out what might the exact issue with the layout of the text without having to see it but here is what this article (Practical Tips for Utilizing Columns of Text in Your Layouts) says about using multiple columns in websites
Many print and web designs you see today employ a simple, single
column design for the main text element. Most printed books use one
column of text per page, although this was not always the trend. Many
older hardcover books featured two columns of text per page; multiple
column formats are still commonly used for books such as dictionaries
and almanacs. Using a single column for type on websites is preferred
so that type is easy to read as you scroll down the page.
Multiple column layouts are best reserved for applications that can be
viewed all at once, such as in print projects or for e-readers.
Multiple column layouts are most commonly used by newspaper and
magazine publishers and in newsletters.
This academic paper (Is Multiple-Column Online Text Better? It Depends!) has this to say about how reading speed might be affected by the use of single and multiple columns
The purpose of this study was to examine how multiple columns and text
justification impact online reading in terms of reading speed,
comprehension, and satisfaction of a narrative passage. Results from
this study showed that reading speed was significantly faster for
two-column full-justified text than for one-column full-justified
text. Post-hoc analyses showed that it was the fastest readers that
benefited the most from this format.
Slower readers showed their fastest reading and highest reading
efficiency at the one-column left-justification condition. This may be
because the very short lines impeded the reader’s ability to take in
an optimal amount of information at each fixation. Gutherie & Wigfield
(2000) assert that a slow reader may lose all information about the
beginning of a sentence from short-term memory before he or she has
read to the end. Slow readers may also have had difficulty "keeping
their place" with the multiple line length conditions for this same
reason.
Given below is a graph of the relative reading speed across multiple columns from this article
With regards to your comment of
Also, this article was long enough that I had to scroll back to the
top after I finished the left column to read the right. Is this as bad
for usability as I think it is?
I would definitely agree since you are have to do a sudden transition to a center point in the screen while moving your eyes from bottom to top and while reading ensure that your scan starts from the central point and not from the extreme left. With regards to the optimal amount of text per paragraph,check out this excerpt from this article about Readability
Blocks of text should not be too long or too wide.
When paragraphs get long, they’re harder to read because there’s less
whitespace. Whitespace gives paragraphs shape, which acts like visual
bearings, making it easier to find your place, and to find the start
of the next line. Using more, smaller paragraphs suits web content
particularly, because it lets you subtly highlight more useful
phrases, by putting them in their own paragraph, or starting a new
paragraph.
For similar reasons, long lines (wide paragraphs) are slower and
harder to read than narrower ones. Lines of around 100 characters
present neat bite-size chunks of text that can easily be decoded, and
also make it really easy to scan round to the start of the next line.
