I'd like to discuss some future possibilities for these two civs. More specifically, the Chinese have something I that think would be better suited for the Vikings
Chinese
Movement Speed Bonus - Applies to Rocket Carts / Does not apply directly to the Fire Galley-line, but is preserved as a part of Dragon Ships
So Rocket Carts move 5% faster in the Castle Age & 10% faster in Imperial. The Chinese don't get Siege Engineers, but the movement speed should help them cover more ground to offset that. Fire Ships don't move any faster, but Dragon Ships do so innately
The idea is to shift them completely towards being a Fire Lancer & Rocket Cart civ
UT2 'Rocketry' - Base Cost 1000 Food 1000 Gold (instead of 1100 Food 900 Gold) i.e. 850 Food 850 Gold after Discount / Does not give +25% Damage to Scorpions / Additionally, gives the Fire Lancer's Special Attack +25% Damage
The Fire Lancer's special attack's projectiles do 3 & 4 (as Elite) damage per projectile, this will be boosted to 3.75 (rounded up to 4?) & 5. Not a big buff, just a little flavour addition
They lose the boost for Scorpions as it feels redundant with Rocket Carts also benefiting from the tech ever since the 3K rework. You either go Rocket Carts or Scorpions, but not both. I'd prefer to keep the Chinese focused on the regional Rocket Cart and give the Scorpions with extra attack to the Vikings instead. The Chinese already get Chu Ko Nus as a source of massive pierce damage output
The focus on Rocket Carts over Scorpions is also in-line with their identity as an expert player's civ
Dragon Ships - Movement Speed 1.794 (instead of 1.56)
Dragon Ships will innately move 15% faster than generic Fast Fire Ships, but the civ does not get Carvel Hull. Currently the movement speed bonus only compensates for Carvel Hull, and only for Fire Ships. This way, their Dragon Ships will be slightly faster than generic Fast Fire Ships, but still slower than Berber ones
Vikings
New Bonus - Battering Ram-line Units & Siege Towers have +50% Garrison Capacity (i.e. +3 & +5 respectively)
While they lost Gambesons, this way they can protect more infantry units by garrisoning them in Rams or Siege Towers. Conversely, their Rams will move faster and output more damage than generic ones with a full garrison
Infantry has +15/20/25% HP in the Feudal/Castle/Imperial Age (instead of +20% starting in the Feudal Age)
The Vikings are strong in the early game and weak in the late game. This tries to address that
They were a big beneficiary of the Men-at-Arms buffs which compounded further with their economy and HP bonus. This way, their infantry units will have 52 HP in the Feudal Age instead of 54
They were always kind of weak in the Imperial Age, but this was further exacerbated with them losing Gambesons for their Champions. With the extra 5% HP, their Champions will have 87 HP (instead of 84), Pikemen will have 69 HP (instead of 66), and Elite Varangian Guards will have 100 HP (instead of 96)
Technology Tree - Lose Cavalier / Gain Keep
They already get all relevant tower techs except for Keeps themselves. I mean Architecture and Arrowslits. This gives them a defensive option in the late-game
While this looks similar to the Danes, I've wanted Keeps for the Vikings ever since they lost Thumb Ring. Once they got Bogsveigar, the plan was to exchange Cavalry Archers for Keeps. With even the Bohemians gaining Mounted Crossbowmen, I don't think the Vikings would be approved to lose MT Xbows, so I'm picking Cavaliers instead. This gives the Vikings a consistent theme of not getting any Imperial Age cavalry line upgrades
UT1 'Chieftains' - Cost 0 Food 600 WOOD 450 Gold (-600 Food +600 Wood) / Additionally, gives Infantry Units +5 Bonus Damage vs. Elephant Units / Additionally, enables Longships to transport 5 Infantry Units
Chieftains regains a new secondary effect of Longships transporting infantry units. Longships (Longboats) were Viking unique units, and the civ should have the best synergy with them even as a regional unit. This can be used to launch small in-land raids with their infantry
UT2 'Bogsveigar' - Research Time 50 Seconds (instead of 40) / Additionally, gives Scorpion-line Units +4 Attack (but no extra Bonus Damage, unlike the Chinese)
This gives them a solid late-game option in addition to Arbalesters. While they do get Siege Engineers unlike the Chinese, they have very poor cavalry and cannot really protect those Scorpions from Bombard Cannons
This has no real basis in history (just like Danish Siege Onagers), and is a reference to the Norse Ballista unit from AoM. Much like how the Danes are an Onager civ, the Vikings would become a Scorpion civ
Berserks - Cost 65 Food 25 Gold (+5 Gold) / Movement Speed 1.1 (instead of 1.05) / Gain Bonus Damage vs. Monks
Base Berserk - Attack 13 (instead of 12) / +3 Bonus Damage each vs. Buildings & Shock Infantry (instead of +2) / Gains +4 Bonus Damage vs. Monks / Regeneration Rate is 30 HP per Minute (instead of 40 like the Elite version) / Line of Sight 4 (instead of 3)
Elite Berserk Research - Cost 1075 Food 575 Gold (+100 Gold)
Elite Berserk - Base HP 64 (instead of 62) i.e. 80 after the +25% HP in Imperial Age Bonus (instead of 74) / Attack 16 (instead of 14) / +4 Bonus Damage each vs. Buildings & Shock Infantry (instead of +3) / Gains +6 Bonus Damage vs. Monks
New Ability - 'Berserkergang' - Berserks double their Regeneration Rate while in Active Combat (i.e. 60/80 HP per Minute as Base/Elite)
It is intended that Berserks should fully take over the 'standard heavy infantry' role from the Militia-line
The anti-Monk bonus is just a flavour or gimmick bonus like Winged Hussars & Kona vs. gunpowder. It is also a reference to the previous effect of Chieftains which let Berserks loot 20 Gold from killed Monks. They're by no means supposed to replace Light Cavalry as Monk counters, but it does mean that non-Elite Berserks two shot Monks without Sanctity (30 HP), and Elite ones likewise two-shot Monks with Sanctity (45 HP)