In all cases you could use the LFG or OOC channels (except for the static dungeons).
People who would keep /listn are the same people that aren't going to mute OOC or LFG channels.
So again use the OOC and LFG channels, there is no need for a /list. If nobody answers you, its probably cause they don't want to.
Alot of people hate getting random /tells sepecially when they may already be /replying to their friends etc.
If you need a wrangle or other buff, ask in the OOC channel is going to be more effective where you can reach everybody at once, rather than sending indivdual /tells to the 5-6 traders who might POSSIBLY be bother to buff you.