Snotling, Piranha,
I'm convinced that hero XP is not split. It has been bothering me for some time, so I ran a battle to check it, and indeed: hero XP is not split. According to Warpedia, heroes should get 250+75 for taking a city with a heavy infantry in it. A Paladin and Dread knight are moving together. They have taken 2 cities together and killed 2 heavy infantry and 1 minotaur. The Dread knight's xp is 749. 250+250+150+75+75 = 800. The Paladin went from 14-- to 1759 for the last battle, city + hv infantry. Certainly not a gain of (250+75)/2. What is going on here? There should be a 50/50 split, but it looks more like a 5% penalty.