The Vlandians, especially the high tier troops, do seem a little bit out of place. The heavy armor and helmets, look more akin to 12th century styles rather than the Norman early 11th century style. If such armor needs to be in the game, it would make more sense to have it be reserved for nobles only, e.g. the plated coat. (the one with the lion)
Another problem is that at this point high tier armor is very much limited in variety, with each culture having around 2 top tier armor designs. That gives high tier troops a sense of uniformity, giving in turn a sense of fanciness (as all sergeants wear a nice red silk cloak).
High tier tier troops (not the elite troops), particularly sergeants, pikemen and champions, should resort to more basic equipment. A full suit of mail was in fact very valuable, so it would be totally sufficient for a top tier infantry troop. Full-face helmets should also be reserved for knights and nobles.
The same could be said for the Empire though. Of course cataphracts can wear the full lamellar suit (however, again, a full set of chainmail supplemented with gambesons was already extremely valuable).
But does every top tier legionary and archer have to wear the same suit of armor and helmet?
The current use of top quality armor is inflationary.
IMO the diversity of armor should be increased, meaning for each tier there are more styles and variants available. Furthermore the cultural top tier armors (Empire lamellar, Vlandia plate etc) should be reserved for nobles and the elite units.