I sometimes use
I-needs-decision to indicate not that no other I-tag applies, but that the right way forward is unclear. i.e., for some given unsound behavior, we might all agree it's a bug, but not on how to fix it. In those cases, there may be another
I- tag that applies. Hence, like
I-nominated, I think that
I-needs-decision is a kind of orthogonal tag.
I'm curious about E-help-wanted vs E-mentor. I don't understand why they would be exclusive?
On a related note, my philosophy on E-mentor lately has been that, if you sign up to E-mentor, you should not only leave a comment indicating your willingness to mentor, you should take the time to write up a comment with enough detail to get somebody started (at least) on fixing the bug, and also leave a few details on how you can be contacted (e.g., your IRC nick), since I think new people to the project won't necessarily know that information. Granted, I've only done this on a few issues, but it seems to be correlated with a much higher rate of people actually following up, so I do think it's something we ought to do.
In general, I think we ought to make adding a write-up part of the expectation for mentoring.