To be honest it is easy to die like that in multiplayer- when someone starts running around your flank it can be hard to turn quick enough. But there are ways in which the combat AI has improved; charging cavalry tend to be very good at going a long way past an enemy to charge back in again, keeping themselves moving fast and getting out of danger. Also spear infantry seems effective at taking cav down (even when stuck among your men in Warband, spear infantry were pretty useless most of the time). Aserai tribesmen are great, with their short spears. They are the lowest tier Aserai unit I think. I was paying 20 gold for the Imperial Recruits, but they are only level 6 troops whereas the Aserai cost 50 gold and are level 11. It makes a big difference.