Multiple sources for each fact is an even better sign of non-NPOV. It means someone is trying too hard to include some fact.
There's no pleasing some people, is there? ;) As long as they are sufficiently different sources, it's generally ok - including lots of sources that are very similar is generally a bad sign, I agree.
I think it is important to note that while all these things may be signs they aren't definitive proofs. Each case should be judged on its own merits. There are plenty of cases where multiple citations for each fact, or completely different citations for every sentence are perfectly acceptable.