I have left a few provinces of the 6th ring, so I've got enough stuff to fight some encounters for quests yet. But I'm concentrating on examining another point at the moment.
There are some heavy differences of the strength of enemy troops in provinces of the same ring, that shouldn't be there! I think, it would be a fair approach for all players, that all provinces of the same ring have an approximately equal strength. This doesn't seem to be the case, if you compare the products of enemy squad size and number of enemies for an encounter, what seems to be the only possible measure method.
As far as I know, the values for an encounter (troops and negotiation costs) are set, when scouting a province. (Just again) I only can speculate about the reasons of differences, it seems to me, that the strength of a province is determined also by your squad size at this moment, what I feel is a really bad idea.