I'm surprised noone has mentioned that the default Sturgia Axe is hands down the best infantry melee weapon in the game. This makes the Varyag the best heavy infantry class in the game because it can also be taken with additional armor + 4 throwing axes.
Northern Heavy Axe - 90 swing speed, 94 damage, 91 length for free.
Imperial Heavy Axe - 98 swing speed, 86 damage, 71 length for a perk slot.
All in all I think the top tier factions are all relatively balanced at the moment ( Sturgia, Vlandia, Empire,Battania, Khuzait ) and any changes without careful consideration could easily throw overall faction greatly out of whack. Unit cost is greatly overlooked in balance for example the Khuzait Spearman is a great cost effective and underrated melee unit for the cost.
Aserai having no direct answer to heavy infantry probably makes them the hardest faction to play right.