Roland certainly did not think that the demons had possessed such incredible power 400 years ago. Otherwise, the Witch Empire would have been eradicated from the Earth within a year or two. The truth was, however, that they had ruled the world for a short decade.
After all, it was impossible to compete against the demons with only a few Extraordinaries. Once every outpost was protected by a similar God's Stone of Retaliation, the witches would have no chance of survival.