One does not simply walk into Dacia...

If I'm using heavy infantry, I avoid that part of the world like the plague. Even asia minor with all its AP ax peoples can be tough if the AI isn't stupid. You should just bring lots and lots of archers. They might even be able to counter attack the various AP units as well. In a reenactment of the Dacian Wars I did with gabheed online, my legionaires got slaughtered but my 400 archer auxilleria slaughtered all the tired ap infantry after they had chewed through about 2000 of my poor poor legionaires.