Tiberius Decimus Maximus said:
It's the brigadier shields that make them so deadly to the Imperial State: it allows them to get close when pikemen and zweihanders can't, and they are masters at hand to hand. That also makes them able to actually take a Imperial State castle without the incredably heavy casualties that other nations get.
Actually, I find the Ormeli to be much more deadly to the IS than the Lion Throne ... sure, they lack the heavy armor, but can rush your battle lines before you finished the formation, disrupt your gunfire by charging directly into your lines and then of course those damn, damn sniper archers ... anyone who fought an Ormeli force before and was put down by a precise arrow into the back from the other side of the battlefield knows what I'm talking about. Contrast that to the rather lightly-armoured State troops and, well, you're in for some fun ...