Chaos magic. Is it necessary?

Against Haven, Chaos is actually a very suitable choice. Considering that the units are tough and the race itself is focused on defense (I don't think I need to explain why), and that the main stats for the hero are "attack" and "defense." People have been writing about the usefulness of the "Lord of Fire" ability and tactics for its application since the original game was released on the HugoCorner forum. There, people who were quite skilled at playing Heroes tested it.
Even if there are Shock or Cold mages in Might and Magic, with well-developed Chaos magic and new druids, the damage will be considerable.