Heart of Chaos

I really liked the scenario. I would also like to know approximately how long it takes to complete.

There is a good strategy – quickly conquer all the cities of the Dark Elf faction, and then start dealing with the Demon. After defeating the Demon, you can gather some troops and then go to defeat Grol in Ur-Kurg. As for Dominion... you definitely need all the artifacts that increase initiative, and a lot of magic defense.