The Viking Huscarles are quite a bit overpowered in my opinion. In vanilla MTW the standard Viking units were some of the best infantry available in early. With these at your disposal there is no real need for FMAA. The Danish Huscarles added to the medieval campaign by the VI expansion seem to inbalance the game.

I was playing a VI campaign as the picts (again!) a few days ago, which I gave up on eventually. The Vikings invaded Domon with all their royals and I decided to try and isolate them there and counter attack, and began sinking as many of their longboats as possible. This took a while of course. Eventually I sent an aprox 800 strong force of pictish cavarly (+1 valour) crossbows, celtic warriors (+1 valour) and some spearmen to deal with an approx 200 strong force of huscarles and thralls. The crossbows shot the 1 complete huscarle unit down to about 70-80 men. Then they pulled back, the Celtic warriors (about 2 units) then charged at them downhill, and the Pictish cavalry flanked (2 units). It took a while for the thralls and another battered unit of huscarles to join up, but when they had done, the first unit had done it's work, and just a handful of my men were routing off the field...

All my tactics seemed fine, but these supermen don't care about tactics. I've charged huscarles at Feudal Knights uphill and won easily. The problem is that they kill so much and gain valour quite quickly, they're also elite, so routing is rarely an issue. Add a six star general to that and you've got an almost unstoppable killing machine.