I jumped on to make a new thread about most of these points, so I will just add it to this thread instead.
I have uninstalled FE. Not that it is a bad game, not at all, but because this game is so much better that it is the only one I need. It is difficult to say exactly why it is so much better, because if I list the fundamental changes, the swarm and tactical changes, the hero leveling changes, the quests...it just isn't describing the new feeling of the game.
OP mentioned pacing, and I think that is a large part of it. Maybe it is the HUGE map?
I have two very well developed cities (I am soooo happy smaller number of cities is viable now), and my army of one sov plus two units slowly became a large army of 3 heroes (got that quest-based badass with the hammer..the one who CRUSHES you and you hope you survive...) plus two, then three units....
Then I created a new unit that, since they are Kraxis, have the ability to really stand fast in defense, are well armored spearmen that regenerate a HP when they land an attack. I got a couple of these going, and broke off my quest champion to start a new army stack, and filled it with these created units plus other types of troops. Recently, I got yet another hero, and have started a third army stack, though this one, since the hero has a -10% unrest, is sitting in my capitol, slowly gaining experience through the adventures guild until I need that stack.
I have the monsters on dense and challenging (+1 level? maybe 2), so the exploring of the area around my cities is slow, tough, but incredibly rewarding. Those two stacks are amazingly built up, but not TOO built up.
The pacing of the champion/unit leveling is so perfect. This is a long game so far, with multiple events across the map, with the eclipse, the one where all known factions declare war on each other, had a plague in my main city and recently a fire storm damaged all the uinits on the map and spawned some fire creatues on the map. It is like a story of this world is being created. The plague, of which I chose to quarentine some people, became another two-step quest in its own, and used to be a big even. but it is now history, with multiple other events, both universe events and the interfighting of the other factions, having become more recent history, and the plaugue just becoming a historical memory. I can't tell you how much this adds to the game for me.
The ability to choose your heroes' skills by a visible tree allows you to create a plan for what your army will become in the future. THIS IS HUGE, and I am not sure people quite understand the implication yet. We're talking, you can choose a path for your hero, then turn around and create units with specific traits and roles that complement or contrast your plan for the hero (go + Army high accuracy in hero, then create a bunch of defensive counter-attacking swordsmen with regen per hit). The new tactical maps strongly support this.
Speaking of those new tactical maps and starting in each other's jocks, I have groaned and smacked my forehead after moving a unit, then realizing I opened a path for the enemy to swarm a weak or low Hp character, knowing that I effed up and will lose that unit. So now I actually pay attention to the individual square to which I have to move each unit. This helps with defense against swarm, redirecting enemy units, setting up a swarm or opening paths for my mounted units to get through their lines to get to the back and take out their archers/casters. This is amazing!
I LOOK for tactical battles so I can play them out, and I develop each army seperately, with its own unique way of fighting, and will even bring in a certain army to take out a specific toughass enemy unit, because I know the "identity" of the army nearest to it won'[t work well against it (I usually start with a defensive/counter-attacking with ranged army, and an offensive, swarming crazy melee group, usually with a defender hero). the crazy thing is that the game just sort of sets this up where this feels like the natural way to play. With Elemental for sure, and less so, but still with FE, I would create these elaborate schemes, but they really didn't matter. Now you win or lose a tactical battle by your army makeup, which is very much in your control, and your decisions on the battlefield. Even if you vastly outnumber them, the swarm ability makes it so they could still cost you dearly by taking out, or at least greatly weaking a prized unit (thus making you have to sit around the adventure map healing, or God help you if you get attacked with that weak prized unit). Tactical battles matter now. they are tantilizingly close to being their own, whole, game within a game.
Give it a try, huge map with dense, challening, monsters. I really gives the game a whole new feeling.