Anyone can beat this scenario on Deity using this guide. Yes, Deity! It's super easy. Play any of the three Viking civs/leaders for the God of the Sea achievement. You score victory points (VPs) in a variety of ways:

• Finding Vinland.
  
• Pilaging
  
• Trade
  
• Empire (population & cities)

Located on the western edge of the map, you will find Vinland, in the New World.

Save your gold and patronize (i.e. buy) Great Admirals and send them west to "activate" near Vinland for a ton of VP. 1000VP for the first. 500VP, 300VP and 100VP thereafter.

Easy VPs!

You will need to research Knarrs to cross the oceans. Actively pursue this technology and related civics to get there ASAP.

Viking Longships have a special promotion allowing them to pillage improvements and districts from the sea. Coastal Raid. (You can even capture workers and settlers this way!)

You get 50VP for every tile pillaged before you convert to Catholism. 10VP afterwards.

As soon as you get the policies Raid and Sack, plunder even more gold and faith!

Each trade route slot you have grants you 25VP.

Build Harbours and Commercial districts in your cities. And don't forget to trade!

In the mid to late game the governments Theocracy and Merchant Republic will allow you to mobilise a huge army from your amassed gold & faith to expand your Empire and conquer distant rivals! (More cities means more trade routes).

For every population you get 10VP before you adopt Catholism. 50VP per population afterwards. For every city you score 25VP.

As Norway think about settling Iceland and Greenland for whale and ivory(!).
Sweden can settle across Eastern Europe towards the Mediterranean for truffles and murcury.
Denmark can expand to either.

After your cities convert to Catholism (when you unlock Monotheism) amass a Berserker horde and go capture a few cities. There are plenty of city states up for grabs. England. Iberia, Byzantium and France.