I wish to point out two balancing issues that were greatly aggravated by the changes in the research costs. I dunno if I am right here so if I should utter my concerns elsewhere just say so.
1. The priests of winter come a little earlier and last much longer (due to the much later champions). They have been imba ever since due to their insane strength of 7, auto-xp and strength 5 ice-elementals (with time they crack just about any city defense around turn 120, being turn 100 for others due to stasis).
Possible solutions:
a) Shift the ritual to fanatism. It's worth it.
b) Weaken the Priests (game would lose a lot of "flavour")
c) Greatly increase Hammer costs of ritual
d) Connect a negative effect to the ritual (e.g. large diplomatic malus "you revive the lore of the god of stasis" or whatever)
2. AV becomes even more insane compared to any other path: Get AV, go for Fanatism, when it takes you 15 turns to complete it, switch to the demonic pact, after you have it, immediately build the grimoire and resume fanatism, get Demon-Tech with grimoire = Mardero + 4 Agares-Beasts before turn 250. Due to cost increase on champions this becomes highly problematic (all numbers on highest difficulty):
Champions: 2800 + 4550 = 7350
AV: 630 + 525 + 490 + 1400 = 3045
Fana+Pact: 1400 + 560 + 3150 + 2100 = 7210
->roughly 3000 res + build time = 15 + 5 turns after other players get champions, you have Mardero (ST:14), 4 Agares-Beasts (ST:16) and some of the insane AV priests. And then for a loooooooooooong time champions will be the strongest challenge coming across. Note additionally that with AV+Priest-tech (=4445 res-points) you get champion-strength units which are only 3/4 the cost, as you can heal(!) diseased corpses.
Possible solutions:
a) Delete the grimoire. It is imba and sucks.
b) Completely change the grimoire (e.g. you can cast a random "demonic" spell every 10 turns, always with the slight risk of it going badly wrong, i.e. barbarian demon. That would make it clearly a Hyborem-Wonder because of his peace with barbs, which I would consider a good "flavour change")
c) Change Grimoire gradually (e.g. it gives 5000 free tech points, that's roughly the points you invest to get there, which can be used to get ~40% of the demon-tech or if you like can get you a number of cheaper techs you can skip before to get AV even faster)
Otherwise I really appreciate the changes, as they
a) slightly weaken the lanun,
b) greatly balance the svart starting-tech-advantage,
c) give sheaim a little edge by increasing the importance of pyre zombies and giving them time to get their ****ing expensive portals,
d) giving the calabim an edge, as their vamps now come well in advance of the former dreaded champs (with higher base strength),
e) make the rangers no longer obsolete,
f) make bow-riders an option, thus strengthening the Hippus-Horselords,
g) make the priests valuable beyond their casting abilities as they now come well in advance of champs.
I dunno how much of these often very heavy balancing changes were intended. Just wanted to point out some (there are lots more, I have not yet analysed) of them.