it seems you confused the instances related to quests with the "leveling astral"
just enter the instance, press P and summon mercenaries (mercenary contract skill), end - no silly waiting for anyone
poster above me is correct, there is NO autosearch for that (mercenaries costs are close to 0)
the "leveling astral" is different, you need 6 players, 1 tank 1 heal + any aspect Lv3, you need to be in a grp and then start it
there are 2 sorts of, (23-50 and 51-69)
if you keep the sings of exp you gain you can even level to 75 with it theoretically
its a fast way of leveling but finding players is as always a tedious task as there is also NO autosearch for that and there are also NO mercenaries
autosearch is only available for basic endgame "gearup-astral" and will grant you free mercs if no players available
autosearch is also availble for easy endgame raid but wont start if no tank / healer signed and there are no mercs, however strenght of boss at least scales to amount of participants dynamically