Let's start by saying that this was NEVER, EVER said. She is the most powerful of the trio, but that was it.Haerta would be a terrible backstory villain for the Order, not least of all as she's portrayed as mind numbingly powerful, so powerful that Xykon is nothing.
May I say that 6 vs. 1 is an advantage? In addition, the Scribblers had two wizards and a DRUID on their side. Soon fulfilled the roles of melee specialist and tank, forcing Haerta to continually cast defensively. And, of course, Haerta's made of soft, Sneak Attack-able flesh for the halfling.it'll be tough to buy guys weaker than Xykon by a fair way standing up to someone who can probably destroy Xykon in a few rounds tops.
Of course, this wouldn't matter at all if Haerta were epic and they were not. But they WERE epic.