Oeee, speculation ;).
I don't understand the fuss about increased lifespan and other stats, other units will (probably) have increased stats as well; it's all relative as you base your decisions on the stats per unit relative to the stats of others units. It thus does not matter if units are represented by single chess-pieces, bananas, hundreds of bananas, blobs, blocks, or penguins (although I hope these will return in some shape or form).
There appear to be differences that I am less fond of, I am, for instance, less enthused with the use of magic in this game. A great many skills and spells are inherent to the characters in AoW1, the game also allows for an extra turn of tactical manoeuvring at the beginning of each battle. This, in my opinion, is great as you can effectively measure your army to the army of the opposition and calculate your odds. In AoW2 you start fights at a shorter distance so it is likely you won't manoeuvre as much and won't use most of the map; there is also a (new) focus on expanding one's magical domain (in which you can use spells). I like the strategical aspects of this game a lot as I find it less rigid/restricted, it has, however, too great a focus on gold (with which you can hurry the production of units and construction of buildings (both within cities as on the map)). The first thing I disliked in the gameplay video of AoW3 is that very powerful spells affected all units in the battle; magic appeared to decide the outcome of the match more so than the type of units and positioning of units.
Haha, although it will increase the odds fighting a Frost Drake ;). So, much good may come from it as well. (Although it may severely overpower heroes and leaders.) This may diverge the focus of the game as mana would inevitably become as important as gold. It may also prevent players from putting together stacks that are (near to) impossible to defeat. And, as you may need to develop spells against certain enemies, it becomes more important to establish and maintain diplomatic relations as it may become necessary to communicate with allies as regards strategic and tactical manoeuvring.
To be honest, I really dislike to see 24 or more enemy units move individually each turn in a battle. It consumes time and it is extremely boring. I do, however, enjoy the positioning of units whichever way I prefer. So I receive these 'insights' and speculations with mixed feelings. Perhaps they could have improved the speed of the game without decreasing the manoeuvrability and possibility to position units in the manner you prefer. For instance by moving all (or groups of) non-attacking units at the same time.