Well, if the problem is with everyone else... it is still more professional to do it through BCC.
What is BCC? Blind Carbon Copy.
It's almost like chain email. It's a matter of privacy.
For instance, I want to share a joke with my friends. Some of my friends don't know each other, but if I send it to all of my friends without using BCC... they all will be able to see each other's email address. That's a violation of their privacies. By using BCC, I forward the joke to myself and BCC it to everyone else. Now, all my friends see that the email was send to me and themselves without seeing anyone else's email addresses.
Now, back to this issue... it's similar. If BCC was used and the email was done in a neutral point of view (no finger-pointing at anyone in particular) and was done in BCC, no one will know who else is involved. Since this email was sent to everyone without using BCC, everyone knows everyone else who has done the same thing. Since this was sent to students as well, then the staff's private email addresses were revealed to students... a big no-no.
So, it's still better to address professional concerns as one-on-one... or in private.
Let's say that I have a few students and faculty members giving me the same problem with communication. What I would probably do is... "Lately, I've been neglected when it came to communication from you. When you have something to say to me, I would appreciate it if you would say it to me directly instead of through my assistant or aide. If you aren't sure if you can sign it to me, then you can at least email me or write it down on paper. By telling everything to my assistant or aide instead of me, you're making it obvious that I can't handle things on my own and that you are reluctant to approach me. This is what I would probably call "unprofessional". So, I would appreciate it if you would communicate with me directly from now on. Thank you." (Notice how I didn't mention any particular times or dates of the incident and no specific names were mentioned?) Now, this is an issue I would use with my staff. So, I send this email to myself and BCC it to the staff members... only those who I have the issue with. Now, I need to resolve it with the students. I can simply bring it up during my next class as if I am telling everyone and am not singling anyone out. Or, I can do it directly with those specific students through email. "Lately, I've noticed in class that I have been neglected when it came to communication from you. When you have something to say to me, I would appreciate it if you would say it to me directly instead of through my assistant or aide. If you aren't sure if you can sign it to me, then you can at least email me or write it down on paper. You can also wait until after class and tell me in private. By telling everything to my assistant or aide instead of me, you're making it obvious that you are reluctant to approach me. It would really help me do my job better as a teacher if you would work with me instead of around me. Thanks." (Notice how I didn't mention any particular times or dates of the incident and no specific names were mentioned? Also, I mentioned "class"... which is more appropriate for a student environment.)
