I am running the most recent version of the game and came across a very annoying bug, especially if your sovereign likes to ride horses.
Whenever a champion on a horse is attacked, its takes 8 seconds to counterattack. It does this every time he is attacked. Only when a champion is on a horse does it happen; take away the horse, and the counterattack is immediate.
I did a complete restart and started a new game to verify it; same thing happens, so I'm pretty sure its not just on my end. Anyone else have this problem?