It is not just Dark Sorcerer (which is now marked as 'Epic' properly.)
For example, in one of my very late game, my sov, who is Life-Water-Air Archmage with some additional spells gained from quests, is still 'weak'. By looks of it, he is. He has some Hp, but very low attack damage with just dagger and ok-ish armor. So the game labeled him as 'weak'.
The problem is he is not 'weak' at all.
He can kill hundreds of units with Blizzard in tactical battle. He does same in strategic map with different spell. (which actually does FAR more damage, since it is total of 9 tiles affected by the skill) With same spell he can permanently destroy any external improvements within his faction's influence range if needed.
He can teleport to great distance with just only 1 turn, BOTH in tactical combat map AND strategic map.
He can instantly create a unit from a city with just 80 mana, which would had been required thousands of golds to do so for very late game troops.
One of his single target damage spell which does nearly 400 damage, enough to kill a dragon in one shot (even if the dragon resisted). And it is not even delayed skill like Storm or Fireball.
Finally, as long as mana does not drain first, he can make any unit completely invulnerable from damage!
As you see, his direct influence is already over the top, and this is even before we are talking about his indirect spells like affecting research and other stuffs.
He is clearly as powerful as a full stack of poison dragons (the most powerful dragon).. Wait, to think again, he is even more powerful than those 9 dragons! There should be 'Godlike' above 'Epic' and he should be on that category.
It is not just mage sov problem, Once I saw Alter declaring war on Krax, Alter had a hundreds of units and Krax had much fewer. The problem was that Alter's units were pretty basic while Krax's ones are properly equipped with spears and shields. Alter had 600 power rating while Krax had 200. After some turns, Krax had gotten into 300 while Alter went down to 100.
I think this power rating problem should be fixed asap, since a lot of AI behavior is based on power rating, and with this being broken, whole AI is broken until it is fixed.