A good indicator used to be to look at the ID's but I'm not so sure that works now. The playerbase has changed so much now and they are accepted at face value.
Can you not think of any group that were set up to fight specific groups, npc factions or houses?
Any places where lots of combat took place that don't now?
Who fought there and for what?
What was the RP behind the different encounters there?
Was it solid RP or just an excuse?
You'd know what kind of encounter it was the moment you came upon it.
One type is generally interesting and fun, the other gets boring and linear in a very short time.