I successfully defended quite a few times too. Once I was hit by two full stacks and I still shot them to pieces. The lancers were certainly not passive but they seemed confused by subtle arrangements, which depends on the terrain. It is good to read their mood.

It's not all about the passive bug, since I did receive charges when I messed up, though they can be withstood by my 6-7 spearmen (since I sacrifice my crossbows, but not when I am retreating) and my horses and Standard. After that however, I always have the discipline to retreat after killign the general, my formation decimated.

I lose more battles but I win the war, by goign after what makes the Mongols really strong.

Its knowing what triggers the Mongols to charge and what triggers them to shoot it out with you, even when the game is patched. For many forget that the archery aspect of Mongols is one of its prime attacks, so even without the passive bug it will choose to shoot it out with you with the right motivation. That's when you grind them to the ground.

Make the right moves. Any attempt to outflank it even on the defensive will invite a mass movement and increases the chances of an all out attack. Any too big movements will invite harsh retaliation. Stand your ground even when the horse archers charge to within feet of you and do not move!

I also don't shoot the lancers counting on the passive bug, since the other Mongol archers are still firing at me. It's not as clear-cut as the passive bug. I also nearly always have very few bolts left to target them anyway, a few volleys concentrated on the lancers nearest the general and I hit the general with all my spears while the horses distract the lancers furtherest away from them. They also seem to go for my tempting Standard and that ties thigns up too. Timign and distraction are important when your troops are as mediocre as mine.

This is by no means a manual on how to do things, just a way I explored to play and seemed to work. I will add a post about usign gun artillery with the formation above next.