The point is that the hero stacks should be seperate. At this point all I see is rhetoric as to why we should have no XP split... I played it with no XP split, wasn't anymore fun, in fact I just kept only one stack of units until I couldn't hold anymore, and then filled up another stack... it was less strategic and I got bored quickly (and still didn't get the XP I was hoping it would provide, just not enough lairs for that).
And I played it with the XP split. A full huge map campaign. Challenging. Many monsters. 6 separate armies at the end. It was not fun. I found that an army of three units is all that is needed for most encounters. Including the last one.
Just upgrade when you feel it necessary (upgraded 2 times I think). Stash heroes in cities for fear of losing them in a combat ; they are so pathetically weak! Not using many spells (since so few heroes were around). Well, for fun, some strategic spells on enemy cities, for what it mattered... Not that it made a difference. And of course those usefull spells on your cities ; these make a difference. Just smashing with bands of trained troops, always with the same tactics because troops have so few abilities...
I finished the game by quest, with three trained units. Oh yeah! Grandiose! Feels heroic. For the troops that is. Not the heroes watching from the nearest tavern. Well, I lie; they were four. The sovereign was there. Mostly watching: ranged troops would do about 100 damage every shot. The dragon died real fast. No way heroes would have done that. I remember another game when so called stack of doom did work. Did the same combat with only heroes.It was long and involved some adrenaline when the tank got too low or when the dragon did blow fire. Of course, in both instances I did win. But then stack of doom felt much much better!
So yes, given the choice, I prefer the so called stack of doom game! Just keeping all heroes alive in a combat is a challenge. By contrast, losing a trained troop is only slightly annoying. Using heroes in a complementary way is interesting ; do I cast that fireball now with this hero, for whom it is not very efficient and expensie, or do I wait the next one for some other spell ? Do I attack with that hero in bad shape, risking losing him if he cannot kill the target, or do I take the risk of another attack by the monster, which might be fatal to another hero ? How much mana can I afford to burn with that combat if I am to continue progressing at a serious rate ? With the so called stack of doom, I at least have choices and fun even if I know I'll win.
And anyway, unless you're playing over challenging (well, I suppose at least), you know you're going to win. So the point is how fun is the journey there...
PS: I actually led each army with a hero of course. Who remained inactive during all encounters, excpet the rare one specialized in fire who would occasionaly cast damaging spells, or the ones with slow/haste, who would occasionally cast these spells. The hero was usually irrelevant to the combat (in the sense that his participation was not significant to achieve victory) and would avoid getting in melee range. An assassin could and would go attacking, but he barely scratched enemy units. A commander quicky abonned all troops after getting killed four times because he was so weak he could not carry a decent armor... No ; that's not Legendery Heroes. That's Leeching Heroes, just standing there to get XP.