Just what are those massively thick shields supposed to stop? A cavalry charge? And why are they so small? I guess, because with their thickness, they would be too heavy otherwise?
A viking shield needs to be big enough that it stretches beyond the elbow , so that it can still protect your shoulder while you ram its edge into the opponent's defense. At the same time, it needs to be light enough, so that it can be rotated from side to side effortlessly.
That swinging motion when striking opponents with the shield also seems unnecessary. It simply kills reach. In boxing terms, just throwing a straight is the best way to utilize the shield, there is no need for throwing hooks, since they just have shorter reach and your opponent wouldn't get that close anyway.
There is also that weird stance where he holds the shield flat towards the top and rests the sword against the shoulder. I will just assume, you used sword+buckler fighting to model the animations, because that's where such a stance would be very effective (and also where those uppercut/hook-like shield bashes would fit right in). With a round bossed center-grip shield, there is not much reason
For some information on the difference between buckler fighting and migration period shields, I suggest this video:
https://www.youtube.com/watch?v=dkhpqAGdZPc