1. Which Faction did you play? How does their late game power compare to earlier in the game? What makes that faction feel unique at this point compared to other factions you have gotten to this point in the game?
Custom faction based on alter with binded, uneducated, adpets, heroic, sov with summoner with magic traits. At late game, there really isn't much difference based on faction-related differences. It is based on more of sov/hero specialization (either go mage or warrior) One thing I realized was that air magic is MUST since it is one route allow you to move across map very quickly and it comes later (I think water magic also has global movement ability, but I think it comes much later level)
2. Which technologies do you rush for? Which ones do you avoid? What is the worst payoff in the late game techs? What is the best tech?
Obviously Civic some points on War then focus on Civ and magic. Civ is always the best tech followed by magic, War tech gets better when game goes really late when you are running non-magic army (but again, it hardly happens.)
3. What are is your economy like? How much of each resource are you getting per turn? What is your Faction Power compared to others?
With normal/challenge setting, tax is always zero because most of resources are coming from buildings instead of population anyway (and this fact annoys me so much). When normal, I am on par with other factions. Regardless of the situation, I will eventually get 2x to 5x compared to other factions on both challenge and normal.
4. How many factions did you start with and how many are still alive? How many are able to compete with you? At what difficulty?
Usually large map with full 9 factions, I usually wipe them all out or do diplomatic victory with just 1 or 2 allies. Normally they just can't compete against me (with both normal and challenging). Probably a bit easier with current version with pioneer spamming intentionally gimped for AI side.
5. What kind of armies does the AI have? Are they building powerful armies or wasting their potential in small weakling groups? Did the AI ever use anything larger than a party?
For my games, they actually make full-stacked armies against me, and most of the times better equipped/numberous than me (challenging). I usually maintain the army as just a sov + 1 or 2 heroes + a few meatshield for early to initial late game to counter their army spam. And then when it is able, I also create fully-stacked armies, but at that point, the game is almost over.
6. What do your armies look like? What level are your units? What weapons do you use? What armor? How many heroes do you have?
Again, with cloud walk, I usually run with just a mage sov + 1~2 heroes + meatshield and it works really well til beginning of late game where I eventually need large armies. With binding trait, I can get free elemental armies from shards buildings, tho they get weaker as the game progress. I don't really concern about weapons/armour as long as it is functional and does job for me. 
I don't hire no more than 2 heroes..... but again, thanks to AI spam, most of the heroes are gone from field before I have to chance to meet them.
7. What is your overall opinion of the late game for Fallen Enchantress?
It has huge balance problems (good thing at least there are enough contents. With balance and bugs fixed, this game is good for release.)
(1) Population is hardly a matter now. Too much reliance on buildings.
(2) Pioneer spam.
These two alone suck the all the fun from the game, and really need to be fixed.