We just had a problem where the ubuntu1404 builder was OOMing often and causing builds to fail.  As they failed within a few minutes the builder was given a new buildset to run, which failed, so it got another buildset...

The result was that the build was 90% a failure but it took a while to notice that all the weird failures were on the same builder (instead of some other common cause, such as distro or architecture).

If the autobuilder had a page that summarised the result of the previous N builds per builder, it would have been easy to spot that one builder was failing 100% of the time in the last run whilst the others were either still running or were green.