Maybe, next to Friends, Group, Clan etc tabs, there should be a Guardian tab which shows who the current active Guardian is for your server

which would help a lot with things like:
:

a) if a Guardian is online but not actually on duty, so that they don't get bugged when they're just having fun

b) it also means that players don't have to go through all the online people on the Guardian Clan list before they find someone who's actually available