Regarding Durkon's importance. Up until he found out about the gates during the Azure City arc he was just another random cleric. We have no idea how often he's spoken to his high priest in the time thats passed since they became High Priest, (to say nothing of the previous one). Also Durkon notes during the desert arc that he doesn't think asking Thor for help will do any good, (though i think he says he will try, then of course Haley, Elan, and V get kidnapped and the things occupy their attention so he may never have got the chance)

Also the mission Thor gives Durkon took some real explaining time, if he never normally prepares commune more than once Thor doesn't exactly have the time he need to explain it all to him, (not to mention he can't show him the gravestones which Thor seemed to think as really important). So they absolutely could have spoken in between on rare, (doesn't normally answer Durkon after all), occasions. For that matter the fact that Thor can set a "ringtone" for a specific Cleric implies he has a system in place so that he can talk to specific Clerics of import more regularly. That implies he does talk directly to some of his clerics.