If they just fixed shields where shield speed made any kind of really noticeable difference, this problem would fix itself.
As it stands, a Huscarl has a speed rating of 81. A Knightly heater has 100. However, that speed difference is BARELY noticeable. If people were rewarded more for using faster shields, I think we would see a lot more shield diversity. The Huscarl would then be very useful for say, pushing into a castle's walls and something like the Knightly Heater would be great for just general fighting.
If people switched to the faster lighter shields -which also can die in about 2 axe hits- I think we'd also have less people complaining about shields.