I think the advy skill, among other things, determines how often you see rogue groups when hunting. E.g. a skilled advy will have a good chance of finding monsters when "there are some rumours about undead", where a less skilled advy will need "many reliable reports", or something 
Yes, this would make sense.
I think it also has an effect on item gathering, and perhaps even on repairing items/finding sages. The latter two being pretty improbable though.
If it did affect gathering, I wonder if item gathering would increased adventurer skill? I know it tells you when it increases from hunting, but if it increases when gathering, there is no message. I somehow suspect it does not increase. My adventuring skill would be 100 if it did (not that there is any way that I can tell what it is...) In theory anything that uses a skill should also increase it, however.
Maybe higher adventuring skill allows you shorter travel times as well? That should be easily confirmed
Now that you mention it, I recall hearing this before somewhere. Definitely merits investigation.
