Yes, I have the same situation in my current game - my units capped at 100XP, but my Ritualist has over 100XP. His summoned creatures have done some fighting for him though. Love those sand cats!
Continuing with my Raging Barb Adventure...
I have managed to make it to the year 1000. Six of the other eight civs have been wiped out by the barbs.
As expected Sheelba remains due to being at peace with the barbs.
However, I was surprised to see Lanun/Falamar still around and winning the game. Falamar does not possess the BAR trait. And, after my religion spread to 3 of its cities I have been able to keep a close eye on what is going on there.
I have never seen a barb in Falamar's territory. The workers and slaves are busily making improvements without any barb incursions.
On the other hand, every time I think many the bad barbs went away they appear again. Now they are throwing only Lizard Rangers (the sneaks really like parking themselves on inland water and attacking from there - got to get a fireball spell after them) and pesky Barbarian Mercenaries at me. I'm still wondering if there ever really were Barbarian Mercenaries.

The Lizard Rangers have been promoted to Level Five. Although the numbers are not insane like the early game (usually 5-6 at a time), their movement points make them a real nuisance.
Anyway, I have fallen hopelessly behind the other two civs in points and will likely not catch up. It is odd playing a huge map with only 3 civs left, and plenty of open spaces and barbs - although they are building many cities too. But, it is still fun defending my civ (I have only 5 cities) and trying to build improvements while dealing constantly with the barbs.
I still maintain that if you play a civ with the BAR trait and raging barbarians you cannot lose. You can just create a few scouts and let them scout the land without worry while picking off the goodie huts. Then sit back and develop your civ while your buddies, the raging ones, pick off the other civs one by one. You can win a Conquest Victory without ever having to declare war on anyone. Or, if you are bored you can send a few troops to another civ to help the barbs out.
Oh, one more thing. I noticed some of Sheelba's units wandering around with 5 Level promotions. I cannot figure out how they got that high as they are at peace with the barbs and no wars were declared.
Years ago I did some beta testing for Blizzard and I have to say the beta testing for FFH2 has been much more fun!
