I see that devs are not planning to change xp split between heroes. I have to agree that it is a good strategy against stack of doom, however, it is so pitiful when i am getting those cool heroes as giants etc. and then i cannot really use them. Hence proposal: 

a) allow for 2 heroes in group then 3rd one causes xp split

b ) further, put a technology in trees - 3 heroes and no xp penalty, then 4 heroes and no penalty. The first should be middle game tech, other late game

c) or, change a name of game to Legendary HERO in order not to deceive potential clients