I was only playing on M/M (because I was fed up with losing all the time) but given the difficulty of ATW, I'm still a bit proud of myself. The hardest battles were against the angles. They had a couple of full stacks that came out of nowhere at one point, when I had just lost a big battle, and took 2 or 3 cities off me before I recovered. It's a very different game to playing as the germanic factions. With Dumnonia I was relying on heavy cavalry almost exclusively to win my battles. Infantry mostly just held the enemy while my cavalry got behind them.