Giving them the Plate Barding Armor for cavalry and the Siege Engineers for the siege weapons is a clear way. Then remove the bonus of additional projectiles for Galleys and Dromons, and change the Cilician Fleet with the Cilician Engineers that provides Scorpions +2 range, War Galleys/Galleons +1 range, and more projectiles to Dromons.
To be honestly it could be better if possible to try to swap the majority of tech trees between Armenians and Georgians. I have suggested it before. In fact based on the history the Armenians are supposed to be the one featuring cavalry and the Georgians are supposed to be the one featuring infantry. Even players from Armenia do not be satisfied. It’s just like the dev accidentally had named the two civ files reversely and then just chose to left the mistakes.
This time another Armenians vs Vikings game, Tatoh vs Hera. Vikings big lose again.
Not only the Armenians need some adjustments, the Vikings might need a tweak particularly on land.
The Vikings could have a not bad economy but hard to turn the economy into a decent military on land. Maybe the reason is that their economy is not an immediate advantage, needing a while to show the power of Hand Carts, but when reaching the time their military units are awful.
I would like to give them the Siege Onager upgrade, and if needed remove the Siege Ram upgrade in exchange.
For more, introduce Shieldman (or Ulfhedinn/Jofurr) and the Elite to replace the Longsword and later, which was suggested in my latest thread. It could have higher pierce armor.
By the way I would also like to let the Longboat able to fire without turning the direction like the Hussite Wagon. The archers on the deck can just fire backward, not like a ballista on the bow of ship that needs the entire ship turn 180° for firing backward.