Taking york in england when it's still a rebel city, can really change the campain for the better, also I find that getting exocuminacated as denmark, isn't so bad, apart from the Holy roman empire which you will have to fight off (They tend to build mass armys of peseant soldeirs which are easy work for your brave viking boys) Viking warriors are very good, along with norse archers, huscarls and norse swordsmen, these are good all round (In fact sometimes building large armys of norse archers, can be very affective because they are good in melee and ranged combat)