They're not that hard to get, it's true.
However, I did notice that I seem to get guild seals everytime I join someone else's game and then go to my sanctuary. I don't know what determines the amount, but one guy I joined yesterday plopped 370 seals on me... seemingly just for me entering my sanctuary, after a weapons trade. Maybe it has something to do with the last quests the person did, or something even more random (this person happened to have just renewed his Gold account and I think I was the first person to co-op with him after that).
I don't think I have the will to try and figure this one out, but it gave me enough seals to get the remaining level 5 chests on my newish character, through someone else's road to rule, so I was very happy about it.