It seems, the scenario is quite balanced on emperor difficulty and normal speed. It's pretty tough mostly because the AI allies, at least in my game, did not comprehend what they need to do. I played as good elves. For example, one of the allies up north near Calabim, had 2 cities for the whole game apparently losing the starting settler and not receiving any immigrants. The one in the middle built 40+ Priests of Leaves for some reason and twice that amount of rangers and housed them all inside their land attacking mostly with champions. Since I could not gift him copper (cannot give cities our resources, can only receive, I resume this is a feature) and for some reason, he did not connect his own iron or mithril, those champions of strength 6 were slaughtered massively promoting enemy units. Evil elves, on the other hand, were pretty much OK and got a few wonders including one which gives invisibility in your borders and that was pretty unpleasant until I was able to capture it.
Early rush was out of the question since I was researching essentially on my own with very little help from the allies and hence the game lingered for about 270 turns. Good thing, I was able to capture the mirror somehow and this really helped as it was possible to farm 5-6 very experienced assassins. That made the trick. The standard tactics was having 3 mages covered with tigers against enemy assassins casting whirlwind storm on the defenders in the city (mostly crossbowmen, 2-3 per city) while druid was entangling them. This was followed with with horde of assassins of my own finishing when probabilities got over 90% with the elite troops. it was very gory and I sacrificed 150+ assassins to take over all the cities which made it for quite a tedious game. However, as a plus, map was nice, production was huge, and immigrants were quite in abundance later on. I finished with 15 cities close to domination limit.
Mild spoiler on gameplay:
So, to sum it all up:
Pros: nice map
, good plot, I loved the intro and the ending. Very nice development of events (both allies in trouble, had to rush to help them survive in the early game). The scenario is balanced for gameplay.
Cons: ridiculously stupid AI allies, do not understand what they should do, did not help at all, did not react to requests for attacking, left cities undefended while having a horde of troops 3 tiles away. They both wasted their world spell (treant defenders) early in the game when Alexis declared on them but actually, there were no enemy troops attacking them inside their lands so treants were just wondering around for a few turns and then were gone without doing any damage to anything. Immigrants coming a bit too randomly, it might be nice to know when they actually are going to come to prepare extra gold for buying settlers and it would be nice to know how much it would cost, at least approximately. Very tedious warring, too many troops to move around. AI defending very passively, mostly sitting in cities and not trying to counterattack.