TY. on normal settings, i have just as many barbarians as you. destroy dungeons to stop them spawning. Warning though, make sure it is not near your city (if possible destroy one near an enemy city) and have lots of strong troops around it (not required for enemy city option). This is because it spawns tonnes of monsters. If it doesn't get destroyed after five tries, a boss will appear. I got 2 warriors on lvl 3 to get to lvl8 by doing this. On died to a boss though...
Also, one dungeon contains a takeout of Monty Python and the Holy Grail. As soon as a scout/ whatever the first unit of yours to see it sees it, a random event will pop up saying that the dungeon is guarded by white death with big teeth (approx, haven't had this event in a while) This is refering to the rabbit guarding the cave that the monster of aaarrgghh lives in in Monty Pythin and the Holy Grail.
You will have three options. None make you lose your unit and all give an advantage exept run.