First, I really like the DLC, please publish more good stuff (Conquest of Gaul)!
A few observations from my current game as Severus:
-After some turns had passed, I received an option to recruit a new legion in Nisibis. At the time it was besieged, and I did lose control of the city for a really short time, which also resulted in the option disappearing. After recapturing the city, the event hasn't reappeared. Is this WAD? In any case Nisibis seems a strange choice for recruitment grounds, being so close to the border.
-The Roman leader Neratianus Aurelianus appears with a green background color and is also green in the combat resolution screen instead of the usual red. Has he maybe been transferred from the Pescennius side in the original Severus scenario?
-This seem pretty common behaviour in all playthroughs, but again I've noticed that the AI is really keen on recruiting lots of militia units and then spamming the map with these. I do feel that its resources would be better spent by recruiting units with more quality.