I thought it was supposed to let you be on one class while seeking on your preferred class.
However, while trying to play a new class and seek for a party for my CNJ, I never showed up in the search for my preferred class.
For example: I was on my lvl1 THM and set up seek for my lvl50 CNJ. When my husband used the search to find a 50 CNJ, my name did not show up UNLESS I was on my lvl 50 CNJ. While I was on my lvl1 THM, that is all my seek would show up for - lvl1 THM.