It's usually a bad idea to strike with force using what essentially amounts to a spear into a wooden shield, because of the likelihood of it getting stuck (the lance's ability to ignite it with time would be moot when we're talking about split second movements, unless you're suggesting your lance has lightsaber like qualities, which would be far beyond this tier level) which would make it easy for the shield user to disarm the spearman, or at most tangle them up for the necessary time for the swordsman to close. 

It's obviously possible for the scales to be pierced, but when utilized on a shield and held at an angle from the strike it would be difficult for pressure to be exacted in such a way that the point would make purchase. The spear would have to hit the shield/scales head on, or from below, to have the best chance. Obviously Sigurd is not likely to let his shield be hit head on, because Vikings (which is what his fighting style is based off roughly) didn't use shields in that fashion. 

If the lance pierced the scales, I suspect it would break through the wood like I mentioned before so the crowbar motion would be unnecessary, but I wouldn't necessarily call that beneficial.

Also, feel free to look anything I say up, if you find someone disproving me let me know, I'm only running on what I've heard HEMA experts say and what I've read in historical sources. I'm a modern history student predominantly, medieval and ancient histories are a hobby, not my degree.