No, it is not an independent clause. In fact, it isn't even a full clause:
Or our ability to differentiate the useful information from the mistruths.
There is no main verb in this phrase. It's just our ability to do something. This is a nominal phrase, not a clause or a sentence.
There is another issue: the use of or there makes the sentence more complicated, and I would consider it inadvisable. And should have been used, and even and than after a comma. The comma is optional: it is probably frowned upon by some, but it certainly make the sentence easier to read. (Without the comma, remove than.)
The amount of information was increasing much more rapidly than our understanding of what to do with it, and than our ability to differentiate the useful information from the mistruths.
The reason is that the information was increasing more rapidly than our understanding what to do, and it was increasing more rapidly than our ability to differentiate: that's what you get when you fill in the ellipsis. It is both-and, not either-or.
The reason that or was used is here is probably that than suggest an implicit negation: after all, the thing you compare it to ("our understanding") is not increasing more rapidly than the thing compared ("the amount of information"). In older French, a negation would be used after than in the same kind of comparison, as in: "this house is larger than that house isn't". Of course we do not do this in English, but the mental inclination is there. And in negative sentences with as, you woulduse or:
This house is not as large as your house or my house.